Bipolar transistor bias question

Started by billbowden in sci.electronics.design9 months ago 62 replies

I have a switching application where a single bipolar transistor might be used. The AC input is about 300mV and the transistor needs about 700...

I have a switching application where a single bipolar transistor might be used. The AC input is about 300mV and the transistor needs about 700 mV to switch on. My idea is to construct a voltage divider using a diode which will produce about a 600mV drop across the diode and a voltage divider of 2 equal resistors to set the transistor base voltage at about 300 mV so the transistor will sw...


looking for a transistor

Started by Anonymous in sci.electronics.design10 years ago 93 replies

I need to switch some GE #44 lamps from a TTL output. #44 lamps are 6.3 volts at 250 ma, so I'll need a transistor to do the real work....

I need to switch some GE #44 lamps from a TTL output. #44 lamps are 6.3 volts at 250 ma, so I'll need a transistor to do the real work. Unfortunately, it's just a hair too much power for one of the hundreds of surplus 2n2222's I keep around to do almost everything else here. Can someone suggest a small, cheap available transistor that would be appropriate for this use? -- Lee K. Gleason N...


Transistor Tester.

Started by Baron in sci.electronics.design3 years ago 1 reply

Hi Guys, A long time ago I came across and article that described a simple transistor tester. It was based on a multivibrator circuit and...

Hi Guys, A long time ago I came across and article that described a simple transistor tester. It was based on a multivibrator circuit and was able to identify which type "N" or "P" of the device connected to the test terminals. I've googled for "transistor tester" and get lots of hits trying to sell them but not what I'm looking for. Thanks: -- Best Regards: B...


Exhausted

Started by David Eather in sci.electronics.design2 years ago 48 replies

If any kind soul can help... There was a short post/note on SED or SEB about a transistor with a 2.5V max Vebo and another one with 3.0 max...

If any kind soul can help... There was a short post/note on SED or SEB about a transistor with a 2.5V max Vebo and another one with 3.0 max Vebo. I have spent hours looking for the transistors and have run out of options. Does anyone remember which transistor numbers these were? I'm adding transistor junction breakdown noise to a Arduino and they would fit the bill perfectly - an...


Fail to amplify 27mhz rf using mosfet IRF843

Started by Anonymous in sci.electronics.design6 months ago 20 replies

I found old mosfet transistor IRF843, using 20k and 70k resistor, i manage to set the voltage at transistor gate to 3.9 volt and using 1uF to...

I found old mosfet transistor IRF843, using 20k and 70k resistor, i manage to set the voltage at transistor gate to 3.9 volt and using 1uF to channel the 27mhz rf signal to the transistor gate, i manage to get an audio from 8ohm speaker connected to the transistor drain. I'm using about 5.3 volt power supply from transformer. The audio is loud and clear. The mosfet gate can received


Best way to protect a transistor from overcurrent?

Started by CJ in sci.electronics.design8 years ago 29 replies

I have a project that involves using a transistor to drive an external device. The external device requires 500mA and my parts are sized...

I have a project that involves using a transistor to drive an external device. The external device requires 500mA and my parts are sized to handle this fine. My concern is that if the external device fails or is improperly connected, it is going to instantly destroy the transistor. What would be an appropriate method to prevent this? I looked at those resettable fuses, but they aren't ...


Transistor-Transistor TTL Logic and Totem pole output

Started by Patrick Chung in sci.electronics.design2 years ago 7 replies

By combining basic TTL Logic NAND gate with invertors and other gate any logical function can be realized in TTL technology. TTL family of logic...

By combining basic TTL Logic NAND gate with invertors and other gate any logical function can be realized in TTL technology. TTL family of logic circuits is specially empowered with TTL Totem pole output Read more: http://www.cirvirlab.com/index.php/electronic/181-transistor-transistor-ttl-logic.html


Howdy the power to do?

Started by FuGuntje in sci.electronics.design8 years ago 5 replies

Hi, I am Fu Gung, evobiology student from Amobinia. I about the transistor power gain read, and want to amplify the AA cell power of 1.5...

Hi, I am Fu Gung, evobiology student from Amobinia. I about the transistor power gain read, and want to amplify the AA cell power of 1.5 Ampere and 3 Vold with the transistor gain so you will help me drive cars with it. The book has power gain for transistors very high, it says 100 000 and more for MOZFEDS. My problem is that when so much power comes out of the transistor the wires of the t...


Need BFY90 transistor preamp

Started by Jim in sci.electronics.design9 years ago 2 replies

Some time back I remember seeing a schematic and I think pcd artwork for a single transistor 2 meter antenna preamp using a BFY90...

Some time back I remember seeing a schematic and I think pcd artwork for a single transistor 2 meter antenna preamp using a BFY90 transistor. I now have a few of these transistors and have need for a small portable preamp that would cover around 147 to 167 mhz with BNC input and output. I have seen a couple kit designs from Ramsey I think, using other RF transistors, but I am pretty sure...


Need Help with Design

Started by BobP122 in sci.electronics.design10 years ago 25 replies

Hi, Could use some help with configuring a: 1 Battery connected to 2. a Switch (2 contacts) connected to 3. a Transistor(& load) The open...

Hi, Could use some help with configuring a: 1 Battery connected to 2. a Switch (2 contacts) connected to 3. a Transistor(& load) The open switch switch turns on the transistor. The closed switch turns off the transistor. B+ > | | > Transistor (Switch open - Trans. OFF) B+ > H > TrTransistor (Switch closed - Trans. ON) Any Ideas? Thanks BobP


BJT or MOSFET for Current Source Circuit

Started by panfilero in sci.electronics.design4 years ago 28 replies

I'm looking to make a "Current Source" I'd like to supply a maximum of 10A, I'm thinking about putting a transistor at the output of an Op-Amp and...

I'm looking to make a "Current Source" I'd like to supply a maximum of 10A, I'm thinking about putting a transistor at the output of an Op-Amp and using the transistor to pull the 10A through my load. My question is, would I be better off using a MOSFET or a BJT for this (darlington or maybe even IGBT) it really just has to sit there and handle 10A... does this point towards which transistor ha...


A high power RF LDMOS transistor

Started by Michael A. Terrell in sci.electronics.design1 year ago 129 replies

This transistor looks interesting: -- Subject: Spelling Lesson The last four letters in American.........I Can The last four...

This transistor looks interesting: -- Subject: Spelling Lesson The last four letters in American.........I Can The last four letters in Republican.......I Can The last four letters in Democrats.........Rats End of lesson. Test to follow in


Transitor as heater

Started by George Herold in sci.electronics.design4 years ago 62 replies

Transistor as heater/ temp sensor. So in looking for a small heater one idea is to use a transistor as heater. And to take the idea one step...

Transistor as heater/ temp sensor. So in looking for a small heater one idea is to use a transistor as heater. And to take the idea one step further to use the same transistor (sequentially) As first a heater then a temp sensor. So the first question is then how to use it as a heater. I was thinking of controlling the current At some fixed voltage.. something like this, https://www...


High GBW jelly bean transistor

Started by David Eather in sci.electronics.design6 years ago 13 replies

Does anyone have a suggestion for a transistor (npn pref) that has a higher GBW than a BC547 or 2N2222 at 2 - 10 ma?

Does anyone have a suggestion for a transistor (npn pref) that has a higher GBW than a BC547 or 2N2222 at 2 - 10 ma?


Transistor Checker

Started by Anonymous in sci.electronics.design3 years ago 8 replies

OK, I pretty much never used one. When the circuit would come alive, the sc= ope tells you if a transistor is bad. If not, the DVM or ohmmeter...

OK, I pretty much never used one. When the circuit would come alive, the sc= ope tells you if a transistor is bad. If not, the DVM or ohmmeter will. (yu= p, that old, I know others are older and actually want to query them so I c= an make sure not to do what they did) At any rate, the boredom does set in once in a while and go looking for tro= uble. In the B&K 520B transoistor tester, I may...


Huh - 2200V Transistor?

Started by Frithiof Jensen in sci.electronics.design9 years ago 3 replies

Just fell over this looking for something else: A ready-made cascode transistor, like the discrete ones I used in my exam project 25 years ago....

Just fell over this looking for something else: A ready-made cascode transistor, like the discrete ones I used in my exam project 25 years ago. Now, where can I get some Oil to put it in?:) http://www.st.com/stonline/products/literature/ds/12919/stc03de220hv.pdf


Best way for mounting high voltage transistors on heat sink

Started by Saman in sci.electronics.design8 years ago 19 replies

Hello, I have a board that has 8 transistors mounted on a heat sink. each TO-220 transistor(IRF 630) dissipates about 10W. for lower voltages I...

Hello, I have a board that has 8 transistors mounted on a heat sink. each TO-220 transistor(IRF 630) dissipates about 10W. for lower voltages I usually used rubber silicon pads for isolation. I have tested them and they can dissipate up to 15W without making transistor too hot. Now I have a high voltage board. the voltage of metal flange(drain) of each transistor is 100V. I haven't worke...


Search for difficult-to-find transistor

Started by Myauk in sci.electronics.design7 years ago 3 replies

Hello all, My ex-colleague had an old oscilloscope with has C1252 transistors defective, and need replacement. I looked for this part...

Hello all, My ex-colleague had an old oscilloscope with has C1252 transistors defective, and need replacement. I looked for this part number in Google, but it could not be found. Is there anybody who knows this transistor, or has the data sheet, or knows the replacement for it? Thanks in advance Regards


need fast switching transistor

Started by Mark R Rivet in sci.electronics.design9 years ago 16 replies

Hello all, I'm looking for a transistor that can handle around 80volt and has a switching speed, full on to full off of 1nano second or...

Hello all, I'm looking for a transistor that can handle around 80volt and has a switching speed, full on to full off of 1nano second or very close to that. Anyone have a source?


NPN Transistor Question

Started by Jim Thompson in sci.electronics.design2 years ago 34 replies

Being in the I/C biz, I don't keep up very well with what is available in the discrete transistor world. What I'm looking for is a...

Being in the I/C biz, I don't keep up very well with what is available in the discrete transistor world. What I'm looking for is a _readily_available_ NPN, highest fT, VCE < 15V, IC < 10mA Suggestions? Thanks! ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations