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basics | Simple transistor NOT gate
There are 19 messages in this thread.
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Re: Simple transistor NOT gate - Tim Wescott - 2008-02-04 00:55:00
On Sun, 03 Feb 2008 17:46:02 -0800, Allen Bong wrote: > On Feb 4, 9:19Â am, Tim Wescott <t...@seemywebsite.com> wrote: >> On Sun, 03 Feb 2008 16:54:44 -0800, Allen Bong wrote: >> > On Feb 4, 2:29Â am, John Larkin >> > <jjlar...@highNOTlandTHIStechnologyPART.com> wrote: >> >> On Sun, 3 Feb 2008 08:18:12 -0800 (PST), Chris >> >> <cfoley1...@yahoo.com> wrote: >> >> >> >On Feb 3, 1:52Â am, Allen Bong <allenbsf6...@gmail.com> wrote: >> >> >> Hi, >> >> >> >> Is it possible to construct a simple inverter gate using 1 or 2 >> >> >> transistors and resistors? >> >> >> >> I tried the circuit below but it doesn't work at all. >> >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â VCC >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â + >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â | >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â | >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â .-. >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â | | >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â | |4K7 >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â '-' >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â | >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â +------o OUTPUT >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â | >> >> >> Â Â Â Â Â Â Â Â 1K_ Â Â Â Â |/ >> >> >> Â Â Â Â INPUT o-|___|----+---| >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â | Â |> >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â .-. Â Â | >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â | | Â Â | >> >> >> Â Â Â Â Â Â Â Â Â Â 4K7| | Â Â | >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â '-' Â Â | >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â | Â Â | >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â | Â Â | >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â === Â === >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â GND Â GND >> >> >> >> Allen >> >> >> >> (created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de) >> >> >> >You've described a perfect transistor inverter, that should work >> >> >for logic level inputs. Â A couple of things to check: >> >> >> >* Make sure you're using an NPN transistor instead of a PNP, a >> >> >MOSFET, or something else. >> >> >> >* Recheck your wiring, looking particularly at the pinout of the >> >> >transistor. Â It's easy to assume EBC when it's ECB, or vice versa. >> >> >> >* Use a voltmeter to actually measure the voltage at the input. Â If >> >> >you're driving the input from an open collector transistor or gate >> >> >output, no current will be injected into the base of your >> >> >transistor when your logic level is "high". >> >> >> >If you run through these three, the transistor has to be defective. >> >> >Replace it. >> >> >> >You've got the right answer right in front of you. Â Make it work. >> >> >> >Cheers >> >> >Chris >> >> >> Classic RTL gate: should work. >> >> >> But if you used this to drive another such gate, the second gate >> >> would serious load down the output voltage of the first one. You >> >> could juggle the resistor values to reduce this effect. Like >> >> maybe... >> >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â VCC >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â + >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â | >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â | >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â .-. >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â | | >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â | | 1K >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â '-' >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â | >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â +------o OUTPUT >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â | >> >> >> Â Â Â Â Â Â Â Â 10K Â Â Â Â |/ >> >> >> Â Â Â Â INPUT o-|___|----+---| >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â | Â |> >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â .-. Â Â | >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â | | Â Â | >> >> >> Â Â Â Â Â Â Â Â Â Â open| | Â Â | >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â '-' Â Â | >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â | Â Â | >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â | Â Â | >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â === Â === >> >> >> Â Â Â Â Â Â Â Â Â Â Â Â GND Â GND >> >> >> John- Hide quoted text - >> >> >> - Show quoted text -- Hide quoted text - >> >> >> - Show quoted text - >> >> > Thanks very much Richard, Randy, Chris & John, >> >> > The gate was used to replace a 74LS04 TTL inverter used between the >> > output of 74LS138 and the LE input of a 74LS373 latch. Â The clock was >> > about 1.8Mhz. Â During a high the transistor conducts fine but during >> > a low input of short duration, I would not be able to get a high with >> > my logic probe nor the LE is triggered. Â The Vcc is 5V and the >> > transistor is a Japanese 2SC945 general purpose transistor. >> >> > I checked with google for a transistor NOT gate and it used 1K at >> > collector and 10K for the base and input. Â There was no resistor >> > between Base and Emitter. Â And I tried that circuit, it doesn't work >> > too. Â Where can I get the schematics for a RTL or DTL not gate? >> >> > TIA and regards, >> >> > Allen >> >> Plain 'ol transistor circuits can be slooow if you aren't careful. Â You >> should either use a smaller (220 ohm?) resistor on the base, or you >> should use a 220 in series with a 1k in parallel with a cap -- >> something between 100pF and 1nF should do, but I refuse to go through >> the math in my head. >> >> You can get Tiny Logic inverters -- I assume you are purposely avoiding >> surface mount parts? >> >> -- >> Tim Wescott >> Control systems and communications >> consultinghttp://www.wescottdesign.com >> >> Need to learn how to apply control theory in your embedded system? >> "Applied Control Theory for Embedded Systems" by Tim Wescott >> Elsevier/Newnes,http://www.wescottdesign.com/actfes/actfes.html- Hide >> quoted text - >> >> - Show quoted text - > > Is this the circuit you have in mind? > > > > > VCC > | > .-. > | | > | |1K > '-' > | > 10k +------o > ___ |/ > o-|___|-+ -| > | |> > .-. | > | | | > 220| | === > '-' GND > | > +---+ > | | > .-. | > | | --- > 1k| | ---1n > '-' | > | | > +---+ > | > === > GND > > > (created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de) > > Yes, this is just a hobby & fun project and I dont have the gears to > solder a SMD. I am constructing the circuit on a breadboard and if it > works, I would solder it onto a stripboard. > > I saw the inverter SMD on the back of the databook. It was made by > Toshiba and part number is TC4S69F. It was a 1989 databook. > > Allen No no! You want the capacitor in the path from the drive to the gate, to speed up the current into and out of the base: 470pF? ___ .----||-----. o---|___|--+ ___ +--- to base of xistor 220 '---|___|---' 1k If you have enough drive this will even forcibly de-saturate a transistor -- look around on the Zetex web site & you'll find some app notes on this. -- Tim Wescott Control systems and communications consulting http://www.wescottdesign.com Need to learn how to apply control theory in your embedded system? "Applied Control Theory for Embedded Systems" by Tim Wescott Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
Re: Simple transistor NOT gate - Allen Bong - 2008-02-04 07:34:00
On Feb 4, 11:21=A0am, "Bob Monsen" <rcmon...@gmail.com> wrote: > Alan: > =A0 =A0Your transtor is saturating when on, and it is probably very slow t= o come > out of saturation. Try putting a diode from base to collector; that will > keep it from saturating. Here is the circuit: > > VCC --------------------------. > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0.-. > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| | 10k > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| | > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0'-' > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 .--->|----o----- out > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A0 =A0 =A0 | > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A0 =A0 =A0 | > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A0 =A0 =A0 | > =A0 =A0 =A0 =A0 =A0 =A0 1k =A0 =A0 =A0| =A0 =A0 =A0 =A0 | > =A0 =A0 =A0 =A0 =A0 =A0 ___ =A0 =A0 | =A0 =A0 =A0 |/ > =A0in -------|___|----o-------| > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 |> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > GND --------------------------' > (created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de) > > This trick is called a 'baker clamp' for some reason. The diode prevents t= he > transistor from saturating, thereby increasing the speed at which it can > turn off. This circuit probably won't do more than a few MHz, but you neve= r > know. > > Regards, > =A0Bob Monsen Hi Bob, Your circuit works like magic. I am going to read more about this 'baker clamp' diode. Was it mentioned in the AoE? Thanks again for your help! Allen
Re: Simple transistor NOT gate - Allen Bong - 2008-02-04 07:40:00
On Feb 4, 1:55=A0pm, Tim Wescott <t...@seemywebsite.com> wrote: > On Sun, 03 Feb 2008 17:46:02 -0800, Allen Bong wrote: > > On Feb 4, 9:19=A0am, Tim Wescott <t...@seemywebsite.com> wrote: > >> On Sun, 03 Feb 2008 16:54:44 -0800, Allen Bong wrote: > >> > On Feb 4, 2:29=A0am, John Larkin > >> > <jjlar...@highNOTlandTHIStechnologyPART.com> wrote: > >> >> On Sun, 3 Feb 2008 08:18:12 -0800 (PST), Chris > >> >> <cfoley1...@yahoo.com> wrote: > > >> >> >On Feb 3, 1:52=A0am, Allen Bong <allenbsf6...@gmail.com> wrote: > >> >> >> Hi, > > >> >> >> Is it possible to construct a simple inverter gate using 1 or 2 > >> >> >> transistors and resistors? > > >> >> >> I tried the circuit below but it doesn't work at all. > > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0VCC > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 + > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0.-. > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| | > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| |4K7= > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0'-' > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 +----= --o OUTPUT > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 1K_ =A0 =A0 =A0 =A0 |/ > >> >> >> =A0 =A0 =A0 =A0INPUT o-|___|----+---| > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 |> > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0.-. =A0 =A0| > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| | =A0 =A0| > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 4K7| | =A0 =A0| > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0'-' =A0 =A0| > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A0 | > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A0 | > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=3D=3D=3D =A0 =3D= =3D=3D > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0GND =A0 GND > > >> >> >> Allen > > >> >> >> (created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de) > > >> >> >You've described a perfect transistor inverter, that should work > >> >> >for logic level inputs. =A0A couple of things to check: > > >> >> >* Make sure you're using an NPN transistor instead of a PNP, a > >> >> >MOSFET, or something else. > > >> >> >* Recheck your wiring, looking particularly at the pinout of the > >> >> >transistor. =A0It's easy to assume EBC when it's ECB, or vice versa= . > > >> >> >* Use a voltmeter to actually measure the voltage at the input. =A0= If > >> >> >you're driving the input from an open collector transistor or gate > >> >> >output, no current will be injected into the base of your > >> >> >transistor when your logic level is "high". > > >> >> >If you run through these three, the transistor has to be defective.= > >> >> >Replace it. > > >> >> >You've got the right answer right in front of you. =A0Make it work.= > > >> >> >Cheers > >> >> >Chris > > >> >> Classic RTL gate: should work. > > >> >> But if you used this to drive another such gate, the second gate > >> >> would serious load down the output voltage of the first one. You > >> >> could juggle the resistor values to reduce this effect. Like > >> >> maybe... > > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0VCC > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 + > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0.-. > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| | > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| | 1K= > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0'-' > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 +----= --o OUTPUT > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 10K =A0 =A0 =A0 =A0 |/ > >> >> >> =A0 =A0 =A0 =A0INPUT o-|___|----+---| > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 |> > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0.-. =A0 =A0| > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| | =A0 =A0| > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0open| | =A0 =A0| > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0'-' =A0 =A0| > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A0 | > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A0 | > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=3D=3D=3D =A0 =3D= =3D=3D > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0GND =A0 GND > > >> >> John- Hide quoted text - > > >> >> - Show quoted text -- Hide quoted text - > > >> >> - Show quoted text - > > >> > Thanks very much Richard, Randy, Chris & John, > > >> > The gate was used to replace a 74LS04 TTL inverter used between the > >> > output of 74LS138 and the LE input of a 74LS373 latch. =A0The clock w= as > >> > about 1.8Mhz. =A0During a high the transistor conducts fine but durin= g > >> > a low input of short duration, I would not be able to get a high with= > >> > my logic probe nor the LE is triggered. =A0The Vcc is 5V and the > >> > transistor is a Japanese 2SC945 general purpose transistor. > > >> > I checked with google for a transistor NOT gate and it used 1K at > >> > collector and 10K for the base and input. =A0There was no resistor > >> > between Base and Emitter. =A0And I tried that circuit, it doesn't wor= k > >> > too. =A0Where can I get the schematics for a RTL or DTL not gate? > > >> > TIA and regards, > > >> > Allen > > >> Plain 'ol transistor circuits can be slooow if you aren't careful. =A0Y= ou > >> should either use a smaller (220 ohm?) resistor on the base, or you > >> should use a 220 in series with a 1k in parallel with a cap -- > >> something between 100pF and 1nF should do, but I refuse to go through > >> the math in my head. > > >> You can get Tiny Logic inverters -- I assume you are purposely avoiding= > >> surface mount parts? > > >> -- > >> Tim Wescott > >> Control systems and communications > >> consultinghttp://www.wescottdesign.com > > >> Need to learn how to apply control theory in your embedded system? > >> "Applied Control Theory for Embedded Systems" by Tim Wescott > >> Elsevier/Newnes,http://www.wescottdesign.com/actfes/actfes.html-Hide > >> quoted text - > > >> - Show quoted text - > > > Is this the circuit you have in mind? > > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0VCC > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0.-. > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| | > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| |1K > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0'-' > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > > =A0 =A0 =A0 =A0 10k =A0 =A0 =A0 +------o > > =A0 =A0 =A0 =A0 ___ =A0 =A0 |/ > > =A0 =A0 =A0o-|___|-+ -| > > =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0|> > > =A0 =A0 =A0 =A0 =A0 =A0 .-. =A0 | > > =A0 =A0 =A0 =A0 =A0 =A0 | | =A0 | > > =A0 =A0 =A0 =A0 =A0220| | =A0=3D=3D=3D > > =A0 =A0 =A0 =A0 =A0 =A0 '-' =A0GND > > =A0 =A0 =A0 =A0 =A0 =A0 =A0| > > =A0 =A0 =A0 =A0 =A0 =A0 =A0+---+ > > =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 | > > =A0 =A0 =A0 =A0 =A0 =A0 .-. =A0| > > =A0 =A0 =A0 =A0 =A0 =A0 | | --- > > =A0 =A0 =A0 =A0 =A0 1k| | ---1n > > =A0 =A0 =A0 =A0 =A0 =A0 '-' =A0| > > =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 | > > =A0 =A0 =A0 =A0 =A0 =A0 =A0+---+ > > =A0 =A0 =A0 =A0 =A0 =A0 =A0| > > =A0 =A0 =A0 =A0 =A0 =A0 =3D=3D=3D > > =A0 =A0 =A0 =A0 =A0 =A0 GND > > > (created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de) > > > Yes, this is just a hobby & fun project and I dont have the gears to > > solder a SMD. =A0I am constructing the circuit on a breadboard and if it= > > works, I would solder it onto a stripboard. > > > I saw the inverter SMD on the back of the databook. =A0It was made by > > Toshiba and part number is TC4S69F. =A0It was a 1989 databook. > > > Allen > > No no! =A0You want the capacitor in the path from the drive to the gate, t= o > speed up the current into and out of the base: > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0470pF? > =A0 =A0 =A0___ =A0 .----||-----. > o---|___|--+ =A0 =A0___ =A0 =A0+--- to base of xistor > =A0 =A0 =A0220 =A0 '---|___|---' > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A01k > > If you have enough drive this will even forcibly de-saturate a transistor > -- look around on the Zetex web site & you'll find some app notes on this.= > > -- > Tim Wescott > Control systems and communications consultinghttp://www.wescottdesign.com > > Need to learn how to apply control theory in your embedded system? > "Applied Control Theory for Embedded Systems" by Tim Wescott > Elsevier/Newnes,http://www.wescottdesign.com/actfes/actfes.html- Hide quot= ed text - > > - Show quoted text - HI Tim, I tried out the circuit but it doesnt work in my application. What do you meant by "if you have enough drive"? I am driving the circuit with the output of a 74LS138. Does the 74LS138 have enough drive to unsaturate the transistor? I am going to google the Zetex web site to get more info as suggested. Thanks. Allen
Re: Simple transistor NOT gate - Tim Wescott - 2008-02-04 11:37:00
On Mon, 04 Feb 2008 04:40:07 -0800, Allen Bong wrote: It sounds like Bob Monsen's solution worked for you. I've done this with 74HC logic, but I'll be damned if I can remember the specific resistor and capacitor values I used. -- Tim Wescott Control systems and communications consulting http://www.wescottdesign.com Need to learn how to apply control theory in your embedded system? "Applied Control Theory for Embedded Systems" by Tim Wescott Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
Re: Simple transistor NOT gate - JeffM - 2008-02-04 19:40:00
Bob Monsen wrote: >>Your [transistor] is saturating when on, >>and it is probably very slow to come out of saturation. >> >> VCC >> | >> .-. >> | | 10k >> | | >> '-' >> | >> .->|---o----- out >> 1k | | >> ___ | |/ >> in --|___|-o----| >> |> >> | >> GND >> Man, Monson put a lot of empty space in his art ...and Google added a lot of crap to it when it got a hold of it. http://groups.google.com/group/sci.electronics.basics/msg/30d98ef099b975e9?dmode=source Could Bob be using an oddball font / character set? ..or is Google "improving" things again? >>This trick is called a 'baker clamp' for some reason. >>The diode prevents the transistor from saturating, >>thereby increasing the speed at which it can turn off. >> Allen Bong wrote: >Your circuit works like magic. I am going to read more >about this 'baker clamp' diode. Was it mentioned in the AoE? Yup. http://books.google.com/?q=Art-of-Electronics+Baker-clamp+saturation "Sorry, this page's content is restricted" I tried anyway so I wouldn't have to walk to the shelf and the F1_1(|<1/\/6 page crashed Gecko. http://validator.w3.org/check?uri=http://books.google.com/books?id=bkOMDgwFA28C&pg=PP1&dq=Art-of-Electronics+bak er-clamp&ei=65qnR6WkAYHgiQH5zr3QBA&sig=jQFnkt5lCVmTHOpUcItQnM-lVVw Failed validation, 579 Errors Opera opened it, but it's true: there's nothing to see there. 8-( Dead-tree version: It's listed in the index: clamp, Baker; page 908.
Re: Simple transistor NOT gate - Allen Bong - 2008-02-04 20:54:00
On Feb 5, 8:40=A0am, JeffM <jef...@email.com> wrote: > Bob Monsen wrote: > >>Your [transistor] is saturating when on, > >>and it is probably very slow to come out of saturation. > > >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0VCC > >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0.-. > >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| | 10k > >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| | > >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0'-' > >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > >> =A0 =A0 =A0 =A0 =A0 =A0.->|---o----- out > >> =A0 =A0 =A0 1k =A0 | =A0 =A0 =A0| > >> =A0 =A0 =A0 ___ =A0| =A0 =A0|/ > >> in --|___|-o----| > >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 |> > >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0GND > > Man, Monson put a lot of empty space in his art > ...and Google added a lot of crap to it when it got a hold of it.http://gr= oups.google.com/group/sci.electronics.basics/msg/30d98ef099b... > Could Bob be using an oddball font / character set? > ..or is Google "improving" things again? > > >>This trick is called a 'baker clamp' for some reason. > >>The diode prevents the transistor from saturating, > >>thereby increasing the speed at which it can turn off. > > Allen Bong wrote: > >Your circuit works like magic. =A0I am going to read more > >about this 'baker clamp' diode. =A0Was it mentioned in the AoE? > > Yup.http://books.google.com/?q=3DArt-of-Electronics+Baker-clamp+saturation= > "Sorry, this page's content is restricted" > I tried anyway so I wouldn't have to walk to the shelf > and the F1_1(|<1/\/6 page crashed Gecko.http://validator.w3.org/check?uri= =3Dhttp://books.google.com/books?id=3Dbk... > Failed validation, 579 Errors > > Opera opened it, but it's true: there's nothing to see there. 8-( > > Dead-tree version: =A0It's listed in the index: clamp, Baker; page 908.- H= ide quoted text - > > - Show quoted text - Hi, you're right! My copy of AoE does have a description on Baker Clamp on Page 584 and also a full chapter on the 8085 micro too. What a find! Looks like the book was sitting in my book shelf for toooooo long and I'm going to reread it from the begining again. Cheers, Allen
Re: Simple transistor NOT gate - Rich Grise - 2008-02-06 19:25:00
On Mon, 04 Feb 2008 17:54:09 -0800, Allen Bong wrote: > Hi, you're right! My copy of AoE does have a description on Baker > Clamp on Page 584 and also a full chapter on the 8085 micro too. What > a find! Looks like the book was sitting in my book shelf for toooooo > long and I'm going to reread it from the begining again. If you want even faster switching, try this: [Bob Monsen drew, but I've modified:] >> >> VCC >> >> | >> >> .-. >> >> | | 10k >> >> added | | >> >> v '-' >> >> ~1nF | >> >> .---||---o-->|--o----- out >> >> | | | >> >> | 1K | | >> >> | ___ | |/ >> >> in -o-|___|--o----| >> >> |> >> >> | >> >> GND Cheers! Rich
Re: Simple transistor NOT gate - Allen Bong - 2008-02-07 16:46:00
On Feb 7, 8:25=A0am, Rich Grise <r...@example.net> wrote: > On Mon, 04 Feb 2008 17:54:09 -0800, Allen Bong wrote: > > Hi, you're right! My copy of AoE does have a description on Baker > > Clamp on Page 584 and also a full chapter on the 8085 micro too. =A0What= > > a find! =A0Looks like the book was sitting in my book shelf for toooooo > > long and I'm going to reread it from the begining again. > > If you want even faster switching, try this: > [Bob Monsen drew, but I've modified:] > > >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0VCC > >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0.-. > >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| | 10k > >> >> =A0 =A0 =A0 =A0added=A0 =A0 =A0 =A0| | > >> >> =A0 =A0 =A0 =A0 =A0v=A0 =A0 =A0 =A0 =A0'-' > >> >> =A0 =A0 =A0 =A0~1nF =A0 =A0 =A0 =A0 | > >> >> =A0 =A0 .---||---o-->|--o----- out > >> >> =A0 =A0=A0|=A0 =A0 =A0 =A0 | =A0 =A0 =A0| > >> >> =A0 =A0=A0|=A0 1K =A0=A0 | =A0 =A0 =A0| > >> >> =A0 =A0 | =A0___ =A0=A0| =A0 =A0|/ > >> >> in -o-|___|--o----| > >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 |> > >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0GND > > Cheers! > Rich Thanks Rich, I do have an 8051 and a PIC16F877 SBC working at 12Mhz and 20Mhz resp. I will try out the circuit there. Rgds, Allen
Re: Simple transistor NOT gate - Allen Bong - 2008-02-13 09:05:00
On Feb 4, 1:55=A0pm, Tim Wescott <t...@seemywebsite.com> wrote: > On Sun, 03 Feb 2008 17:46:02 -0800, Allen Bong wrote: > > On Feb 4, 9:19=A0am, Tim Wescott <t...@seemywebsite.com> wrote: > >> On Sun, 03 Feb 2008 16:54:44 -0800, Allen Bong wrote: > >> > On Feb 4, 2:29=A0am, John Larkin > >> > <jjlar...@highNOTlandTHIStechnologyPART.com> wrote: > >> >> On Sun, 3 Feb 2008 08:18:12 -0800 (PST), Chris > >> >> <cfoley1...@yahoo.com> wrote: > > >> >> >On Feb 3, 1:52=A0am, Allen Bong <allenbsf6...@gmail.com> wrote: > >> >> >> Hi, > > >> >> >> Is it possible to construct a simple inverter gate using 1 or 2 > >> >> >> transistors and resistors? > > >> >> >> I tried the circuit below but it doesn't work at all. > > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0VCC > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 + > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0.-. > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| | > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| |4K7= > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0'-' > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 +----= --o OUTPUT > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 1K_ =A0 =A0 =A0 =A0 |/ > >> >> >> =A0 =A0 =A0 =A0INPUT o-|___|----+---| > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 |> > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0.-. =A0 =A0| > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| | =A0 =A0| > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 4K7| | =A0 =A0| > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0'-' =A0 =A0| > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A0 | > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A0 | > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=3D=3D=3D =A0 =3D= =3D=3D > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0GND =A0 GND > > >> >> >> Allen > > >> >> >> (created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de) > > >> >> >You've described a perfect transistor inverter, that should work > >> >> >for logic level inputs. =A0A couple of things to check: > > >> >> >* Make sure you're using an NPN transistor instead of a PNP, a > >> >> >MOSFET, or something else. > > >> >> >* Recheck your wiring, looking particularly at the pinout of the > >> >> >transistor. =A0It's easy to assume EBC when it's ECB, or vice versa= . > > >> >> >* Use a voltmeter to actually measure the voltage at the input. =A0= If > >> >> >you're driving the input from an open collector transistor or gate > >> >> >output, no current will be injected into the base of your > >> >> >transistor when your logic level is "high". > > >> >> >If you run through these three, the transistor has to be defective.= > >> >> >Replace it. > > >> >> >You've got the right answer right in front of you. =A0Make it work.= > > >> >> >Cheers > >> >> >Chris > > >> >> Classic RTL gate: should work. > > >> >> But if you used this to drive another such gate, the second gate > >> >> would serious load down the output voltage of the first one. You > >> >> could juggle the resistor values to reduce this effect. Like > >> >> maybe... > > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0VCC > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 + > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0.-. > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| | > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| | 1K= > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0'-' > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 +----= --o OUTPUT > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 10K =A0 =A0 =A0 =A0 |/ > >> >> >> =A0 =A0 =A0 =A0INPUT o-|___|----+---| > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 |> > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0.-. =A0 =A0| > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| | =A0 =A0| > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0open| | =A0 =A0| > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0'-' =A0 =A0| > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A0 | > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A0 | > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=3D=3D=3D =A0 =3D= =3D=3D > >> >> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0GND =A0 GND > > >> >> John- Hide quoted text - > > >> >> - Show quoted text -- Hide quoted text - > > >> >> - Show quoted text - > > >> > Thanks very much Richard, Randy, Chris & John, > > >> > The gate was used to replace a 74LS04 TTL inverter used between the > >> > output of 74LS138 and the LE input of a 74LS373 latch. =A0The clock w= as > >> > about 1.8Mhz. =A0During a high the transistor conducts fine but durin= g > >> > a low input of short duration, I would not be able to get a high with= > >> > my logic probe nor the LE is triggered. =A0The Vcc is 5V and the > >> > transistor is a Japanese 2SC945 general purpose transistor. > > >> > I checked with google for a transistor NOT gate and it used 1K at > >> > collector and 10K for the base and input. =A0There was no resistor > >> > between Base and Emitter. =A0And I tried that circuit, it doesn't wor= k > >> > too. =A0Where can I get the schematics for a RTL or DTL not gate? > > >> > TIA and regards, > > >> > Allen > > >> Plain 'ol transistor circuits can be slooow if you aren't careful. =A0Y= ou > >> should either use a smaller (220 ohm?) resistor on the base, or you > >> should use a 220 in series with a 1k in parallel with a cap -- > >> something between 100pF and 1nF should do, but I refuse to go through > >> the math in my head. > > >> You can get Tiny Logic inverters -- I assume you are purposely avoiding= > >> surface mount parts? > > >> -- > >> Tim Wescott > >> Control systems and communications > >> consultinghttp://www.wescottdesign.com > > >> Need to learn how to apply control theory in your embedded system? > >> "Applied Control Theory for Embedded Systems" by Tim Wescott > >> Elsevier/Newnes,http://www.wescottdesign.com/actfes/actfes.html-Hide > >> quoted text - > > >> - Show quoted text - > > > Is this the circuit you have in mind? > > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0VCC > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0.-. > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| | > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| |1K > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0'-' > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > > =A0 =A0 =A0 =A0 10k =A0 =A0 =A0 +------o > > =A0 =A0 =A0 =A0 ___ =A0 =A0 |/ > > =A0 =A0 =A0o-|___|-+ -| > > =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0|> > > =A0 =A0 =A0 =A0 =A0 =A0 .-. =A0 | > > =A0 =A0 =A0 =A0 =A0 =A0 | | =A0 | > > =A0 =A0 =A0 =A0 =A0220| | =A0=3D=3D=3D > > =A0 =A0 =A0 =A0 =A0 =A0 '-' =A0GND > > =A0 =A0 =A0 =A0 =A0 =A0 =A0| > > =A0 =A0 =A0 =A0 =A0 =A0 =A0+---+ > > =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 | > > =A0 =A0 =A0 =A0 =A0 =A0 .-. =A0| > > =A0 =A0 =A0 =A0 =A0 =A0 | | --- > > =A0 =A0 =A0 =A0 =A0 1k| | ---1n > > =A0 =A0 =A0 =A0 =A0 =A0 '-' =A0| > > =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 | > > =A0 =A0 =A0 =A0 =A0 =A0 =A0+---+ > > =A0 =A0 =A0 =A0 =A0 =A0 =A0| > > =A0 =A0 =A0 =A0 =A0 =A0 =3D=3D=3D > > =A0 =A0 =A0 =A0 =A0 =A0 GND > > > (created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de) > > > Yes, this is just a hobby & fun project and I dont have the gears to > > solder a SMD. =A0I am constructing the circuit on a breadboard and if it= > > works, I would solder it onto a stripboard. > > > I saw the inverter SMD on the back of the databook. =A0It was made by > > Toshiba and part number is TC4S69F. =A0It was a 1989 databook. > > > Allen > > No no! =A0You want the capacitor in the path from the drive to the gate, t= o > speed up the current into and out of the base: > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0470pF? > =A0 =A0 =A0___ =A0 .----||-----. > o---|___|--+ =A0 =A0___ =A0 =A0+--- to base of xistor > =A0 =A0 =A0220 =A0 '---|___|---' > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A01k > > If you have enough drive this will even forcibly de-saturate a transistor > -- look around on the Zetex web site & you'll find some app notes on this.= > > -- > Tim Wescott > Control systems and communications consultinghttp://www.wescottdesign.com > > Need to learn how to apply control theory in your embedded system? > "Applied Control Theory for Embedded Systems" by Tim Wescott > Elsevier/Newnes,http://www.wescottdesign.com/actfes/actfes.html- Hide quot= ed text - > > - Show quoted text - Hi Tim, I've found the application notes on the zetex web site. It was on P2 & P4 of the pdf file which explains the speeding up of switching, both the capacitor speedup and baker clamp methods are described. http://www.zetex.com/3.0/appnotes/apps/an22.pdf Allen