Forums

0.2MHz - 2MHz step up transformer

Started by Paul Jackson January 22, 2012
amdx wrote:
> > >> > >> If you want 20 ma at 100 volts, I don't think you generator will supply > >> the power you need. > >> If the generator supplies 10V into 50 ohms that is 20 ma. > >> With a 1 to 10 voltage step up you generator would need to supply > >> 200 ma. > > > > > > If Paul's generator is too weak to drive loads under 10ohms then he'd > > need to find or build a staunch buffer. > > > I'll add to that, some signal generators have an amplifier with a very > low output impedance and a series 50 ohm resistor. If you have this type > and want to load it at 10 ohms, make sure the 50 ohm resistor is rated > for the wattage needed, especially if you expect continuous use. I have > seen blacked 50 ohm output resistors. I won't name any HP names. > Mikek
I once had a Wavetek generator die on me when I connected a 50 ohm termination to its "50 ohm" output. Fried an output transistor. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
Phil Hobbs wrote:

> amdx wrote: > >>>> If you want 20 ma at 100 volts, I don't think you generator will supply >>>>the power you need. >>>>If the generator supplies 10V into 50 ohms that is 20 ma. >>>> With a 1 to 10 voltage step up you generator would need to supply >>>>200 ma. >>> >>> >>>If Paul's generator is too weak to drive loads under 10ohms then he'd >>>need to find or build a staunch buffer. >>> >> >> I'll add to that, some signal generators have an amplifier with a very >>low output impedance and a series 50 ohm resistor. If you have this type >>and want to load it at 10 ohms, make sure the 50 ohm resistor is rated >>for the wattage needed, especially if you expect continuous use. I have >>seen blacked 50 ohm output resistors. I won't name any HP names. >> Mikek > > > I once had a Wavetek generator die on me when I connected a 50 ohm > termination to its "50 ohm" output. Fried an output transistor. > > Cheers > > Phil Hobbs
So I assume the warranty must of expired? Jamie
On Sun, 22 Jan 2012 16:13:16 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>amdx wrote: >> >> >> >> >> If you want 20 ma at 100 volts, I don't think you generator will supply >> >> the power you need. >> >> If the generator supplies 10V into 50 ohms that is 20 ma. >> >> With a 1 to 10 voltage step up you generator would need to supply >> >> 200 ma. >> > >> > >> > If Paul's generator is too weak to drive loads under 10ohms then he'd >> > need to find or build a staunch buffer. >> > >> I'll add to that, some signal generators have an amplifier with a very >> low output impedance and a series 50 ohm resistor. If you have this type >> and want to load it at 10 ohms, make sure the 50 ohm resistor is rated >> for the wattage needed, especially if you expect continuous use. I have >> seen blacked 50 ohm output resistors. I won't name any HP names. >> Mikek > >I once had a Wavetek generator die on me when I connected a 50 ohm >termination to its "50 ohm" output. Fried an output transistor. > >Cheers > >Phil Hobbs
The old Waveteks blew up a lot. Fortunately, they were pretty repairable. I have a couple of these. Handy gadgets. https://www.bkprecision.com/products/signal-generators/4003A-4-mhz-sweep-function-generator-with-5-digit-red-led.html John
"Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message 
news:4F1C7BEC.E3925D87@electrooptical.net...
> I once had a Wavetek generator die on me when I connected a 50 ohm > termination to its "50 ohm" output. Fried an output transistor.
Tell me about it.. I fried mine driving a B-E junction... same idea. How can something not be made to drive the rated load? Beats me. They used a weird output stage too, it has an op-amp around it for DC; the fast stuff is AC coupled, a peculiar complementary buffer. I replaced the transistors with some TO-126 parts I had on hand, not nearly as much fT so it hardly does 5MHz from the output proper; I tapped a jack off a testpoint so I can still use a full-bandwidth signal, though it doesn't have attenuation or offset on it. Tim -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
Jamie wrote:
> > Phil Hobbs wrote: > > > amdx wrote: > > > >>>> If you want 20 ma at 100 volts, I don't think you generator will supply > >>>>the power you need. > >>>>If the generator supplies 10V into 50 ohms that is 20 ma. > >>>> With a 1 to 10 voltage step up you generator would need to supply > >>>>200 ma. > >>> > >>> > >>>If Paul's generator is too weak to drive loads under 10ohms then he'd > >>>need to find or build a staunch buffer. > >>> > >> > >> I'll add to that, some signal generators have an amplifier with a very > >>low output impedance and a series 50 ohm resistor. If you have this type > >>and want to load it at 10 ohms, make sure the 50 ohm resistor is rated > >>for the wattage needed, especially if you expect continuous use. I have > >>seen blacked 50 ohm output resistors. I won't name any HP names. > >> Mikek > > > > > > I once had a Wavetek generator die on me when I connected a 50 ohm > > termination to its "50 ohm" output. Fried an output transistor. > > > > Cheers > > > > Phil Hobbs > So I assume the warranty must of expired? > > Jamie
I don't recall. I needed the generator, so I opened it up and put in a beefier transistor. It slowed down the edges a bit, but didn't blow up. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
On Sun, 22 Jan 2012 10:27:38 -0500, Jamie
<jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:

> Being a function generator as the source, I think you better start >thinking of HV amplifiers instead. A DC coupled one to be exact. >
How then would I match the 1K Ohm resistive load? Paul
Paul Jackson wrote:
> > On Sun, 22 Jan 2012 10:27:38 -0500, Jamie > <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote: > > > Being a function generator as the source, I think you better start > >thinking of HV amplifiers instead. A DC coupled one to be exact. > > > > How then would I match the 1K Ohm resistive load? > > Paul
Why do you care about matching the load? The two normal reasons for wanting to match impedances are (1) to get maximum power transfer, and especially (2) to avoid standing waves in a transmission line, which give you weird variations with drive impedance vs frequency. You won't have reflection issues at those frequencies, and if you build an amp, you can have any power level you need, so maximum power transfer isn't an issue. (Maximum power transfer is usually a red herring anyway--as Joerg never tires of pointing out, in an impedance-matched system, half the power is being dissipated in the transmitter, which usually isn't what you want.) Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
On Sun, 22 Jan 2012 10:27:38 -0500, Jamie
<jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:


> Being a function generator as the source, I think you better start >thinking of HV amplifiers instead. A DC coupled one to be exact. >
What would be your opinion of these? http://www.piezomaster.com/ Paul
John Larkin wrote:
> On Sun, 22 Jan 2012 16:13:16 -0500, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> amdx wrote: >>>>> If you want 20 ma at 100 volts, I don't think you generator will supply >>>>> the power you need. >>>>> If the generator supplies 10V into 50 ohms that is 20 ma. >>>>> With a 1 to 10 voltage step up you generator would need to supply >>>>> 200 ma. >>>> >>>> If Paul's generator is too weak to drive loads under 10ohms then he'd >>>> need to find or build a staunch buffer. >>>> >>> I'll add to that, some signal generators have an amplifier with a very >>> low output impedance and a series 50 ohm resistor. If you have this type >>> and want to load it at 10 ohms, make sure the 50 ohm resistor is rated >>> for the wattage needed, especially if you expect continuous use. I have >>> seen blacked 50 ohm output resistors. I won't name any HP names. >>> Mikek >> I once had a Wavetek generator die on me when I connected a 50 ohm >> termination to its "50 ohm" output. Fried an output transistor. >> >> Cheers >> >> Phil Hobbs > > The old Waveteks blew up a lot. Fortunately, they were pretty > repairable. > > I have a couple of these. Handy gadgets. > > https://www.bkprecision.com/products/signal-generators/4003A-4-mhz-sweep-function-generator-with-5-digit-red-led.html >
In my Wavetek 23 it looks like the EPROM died partially. Those things become very uncomfortably hot on the inside. After finding that the EPROM was the problem I took the chicken exit and bought a Chinese 20MHz arb generator. Believe it or not but I never owned an EPROM programmer. -- Regards, Joerg http://www.analogconsultants.com/
Phil Hobbs wrote:
> Paul Jackson wrote: >> On Sun, 22 Jan 2012 10:27:38 -0500, Jamie >> <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote: >> >>> Being a function generator as the source, I think you better start >>> thinking of HV amplifiers instead. A DC coupled one to be exact. >>> >> How then would I match the 1K Ohm resistive load? >> >> Paul > > Why do you care about matching the load? The two normal reasons for > wanting to match impedances are (1) to get maximum power transfer, and > especially (2) to avoid standing waves in a transmission line, which > give you weird variations with drive impedance vs frequency. > > You won't have reflection issues at those frequencies, and if you build > an amp, you can have any power level you need, so maximum power transfer > isn't an issue. (Maximum power transfer is usually a red herring > anyway--as Joerg never tires of pointing out, in an impedance-matched > system, half the power is being dissipated in the transmitter, which > usually isn't what you want.) >
Agree. And if you really wanted to source terminate for some reason and have a 10:1 step-up ratio just hang a resistor in series with the source. 10ohms minus its native output impedance. There is nothing that beat drive power. Except for more drive power. -- Regards, Joerg http://www.analogconsultants.com/