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Transistor Circuits
Transistors:  #'s - C    D - I     J - O     P - S     T - Z

Last Updated: November 30, 2017 10:28 AM

Circuits Designed by Dave Johnson, P.E. :
300v Peak to Peak Signal Generator -  This circuit converts a square wave signal to a +-150 volt output signal with fast 100nS rise and fall times. . . Circuit by David Johnson P.E.-June, 2000

AC/DC relay from Charge Coupled MOSFET -  This circuit acts as an AC/DC relay with a rating up to 50 volts peak and up to 10 amps of current.  The differential oscillator supplies voltage to the gates of the two FETs with good isolation will drawing only 1.5ma of current . . . Hobby Circuit designed by David Johnson P.E.-October, 2005

Astable Multivibrator with Very Low Power -  This classic circuit draws only 200 nanoamps from a 1.5v supply . . . Hobby Circuit designed by David A. Johnson P.E.-June, 2000

Bi-Directional Charge Coupled Powers MOSFET Relay -  The circuit uses an inexpensive C-MOS inverter package and a few small capacitors to drive two power MOS transistors from a 12v to 15v supply.  Since the coupling capacitor values used to drive the FETs are small, the leakage current from the power line . . . Hobby Circuit designed by David Johnson P.E.-June, 2000

characteristics of CMOS Logic Inverter Amplifiers -  This chart shows some of the measured characteristics of three different unbuffered CMOS logic gates, used as voltage amplifiers . . . Hobby Circuit designed by David Johnson P.E.-February, 2002

Charge Coupled Bi-Directional Power MOSFET Relay -  The circuit uses an inexpensive C-MOS inverter package and a few small capacitors to drive two power MOS transistors from a 12v to 15v supply.  Since the coupling capacitor values used to drive the FETs are small, the leakage current from the power line. . . Circuit by David A. Johnson P.E.-June, 2000

Charge Coupled MOSFET Relay #2 -  This circuit acts as an AC/DC relay with a rating up to 50 volts peak and up to 10 amps of current.  The differential oscillator supplies voltage to the gates of the two FETs with good isolation will drawing only 1.5ma of current. . . Circuit by David A. Johnson P.E.-October, 2005

Charge Pump Efficiently Divides Supply Voltage  -  This circuit uses a few FETs and logic devices to down convert a DC voltage to about one half its value. . . Circuit by David Johnson P.E.-July, 2000

Circuit Protects from Battery Polarity Reversal -  This simple circuit can protect a sensitive electronic circuit from an accidental connection of a battery with a reversed polarity.  The N-channel FET connects the electronic device to the battery only when the polarity is correct.  The circuit shown was. . . Circuit by Dave Johnson P.E.-March, 2002

CMOS Logic Inverter Amplifier characteristics -  This chart shows some of the measured characteristics of three different unbuffered CMOS logic gates, used as voltage amplifiers. . . Circuit by Dave Johnson P.E.-February, 2002

Capacitance Proximity Switch
Draws very low power - Ideal for battery-powered applications
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Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

1 Transistor Provides Short-Circuit Protection -  10/16/03  EDN Design Ideas:  in certain DC/DC-converter applications, on-chip, cycle-by-cycle current limit may be insufficient protection to prevent a failure during a short circuit.  A nonsynchronous boost converter provide as a direct path from the input to th __ Circuit Design by Keith Szolusha, Linear Technology Corp, Milpitas, CA

-/+-0.1V Differential Amplifier using Zero Threshold EPAD MOSFETs -  This circuit presents a differential amplifier using Zero Threshold EPAD MOSFETs that oooooperates on 1/- 0.1v supplies.    The schematic diagram is for a single amplifier stage__ Advanced Linear Devices, Inc

12 volt Inverter-Very Basic type -  This circuit will provide a fairly stable "Square Wave" Output Voltage.  Frequency of operation is Mainly determined by the 220 uF Feedback Caps.  Currently about 60 Hz.  Various "off the shelf" transformers can be used. __ Designed by G.L. Chemelec

1-transistor FM Transmitter -  A truly minimalist circuit.  Performance is relatively poor and stability is a problem.  Q1 modulates the signal and acts as an oscillator.  L1 and C5 determine the frequency.  Decrease C5 for a higher frequency and vice-versa.  __ 

2 Transistor Amplifier -  This electronic circuit design shows a simple two transistor amplifier with feedback.  it offers a reasonably high impedance while providing a low output impedance.   __ Designed by Ian Poole

2 Transistor Atomic Frequency Standard -  Pretty ambitious title, wouldn't you say? Well, follow the reasoning: if you lower the voltage on the two-transistor flasher to 1.5 volts, the loop gain drops too low for sustained flashing. (See the circuit below.) But, the circuit is highly regenerative and only needs a very tiny push to get it going. __  Contact:  Charles Wenzel of Wenzel Associates, Inc.

2 transistor FM transmitter / FM bug -  VOYAGER is a super-sensitive FM Radio microphone developed by Talking  Electronics.  The components are all common types of resistors, capacitors and transistors matched so well in this circuit that  amazing  sensitivity and  distance  are obtained.  The name VOYAGER was given to it "because it  goes so far".  We have re-designed the Board and further matched some components  to  suit  the  needs  of  the  classroom.  The result is a superb bug which is compact but powerful, and quite easy to build__ CdS Electronic

2 Transistor LED Flasher -  This 1.5 volt LED fasher runs more than a year on a single 'd" cell and alternately flashes 2 LEDs at about a 1 second rate.  The circuit employs a 74HC14 CMOS hex inverter that will operate at very low voltages (less than 1 volt).  One section is used as a squarewave oscillator (pins 1 and 2) , while the others are wired to produce a short 10mS pulse on alternate edges of the square wave so the LEDs will alternate back and forth.  The output sections each use a capacitor charge pump to increase the voltage for the LEDs __ Designed by Bill Bowden

2 Transistor LED Flasher -  This circuit will flash a bright red LED as an attention getting device or fake care alarm. __ Designed by Bill Bowden

2 Transistor LED Flasher -  This is a classic 2 transistor astable multivibrator.  Many other NPN small signal or switching transistors can be used, including 2N4401, PN2222 or 2N2222 using the circuit on the left.  The circuit can also be inverted using PNP transistors.   __ Designed by Bill's Electronics Reference Library

2 Transistor LED Flasher 1 -  Circuit Only __ Designed by Tony van Roon  VA3AVR

2 Transistor LED Flasher 2 -  This circuit will flash a super-bright LED (5000+ mcd).  Good for fake car alarm or other attention getting device.  Component values are not critical, try anything else first from your junkbox.  Obviously, the 470 ohm resistor (R3) determines the LEDs brightness and limits the current flow to about 20mA.390 ohm can also be used as a save value.  if you decide to go with a green or yellow led, which draw more current, you may want to replace the 470 ohm with an appropriate value.  Flash rate is determined by R2 and C1 __ Designed by Tony van Roon  VA3AVR

2 transistor lights LEDs -  04/09/09  EDN Design Ideas:  A previous Design ideas - describes a circuit that uses an astable multivibrator to drive an LED (Reference 1].  The circuit in Figure 1 uses a simpler alternative approach.  The circuit uses a 2N3904 NPN transistor and a 2N3906 PNP trans __ Circuit Design by Barry A Tigner, Michigan State University, East Lansing, MI

2 transistor replaces IC -  02/07/02 EDN Design Ideas:  Linear Technology's recently introduced LTC4300 chip buffers i2C clock and data lines to and from a hot-swappable card.  This task is difficult because the IC must work bidirectionally, meaning that you can simultaneously and actively drive both side as.  However, as is sometimes the case, you can replace a complicated circuit by a simple one without much loss of performance __ Circuit Design by Jim Hagerman, Hagerman Technology, Honolulu, HI

2 Transistor replaces IC (Hagtech) -  I am always impressed with the way semiconductor manufacturers go out of their way to make the end designer’s job easier.  One example is the LTC4300 recently introduced by Linear Technology.   __ Designed by Jim Haggerman, Hagerman Technology LLC

2 Transistor Transmitter -  A compact 2 transistor transmitter for use at VHF frequencies.   __ Designed by Rob van der Weijden

2 transistors form bidirectional level translator -  11/07/96 EDN Design Ideas:  This example illustrates a translation from 5 to 3V, but it can accommodate almost any other voltage levels, provided the logic-low levels are equal (usually0V].  Translations from 1 to 100V are possible, albeit rather slow.  The key to this circuit is the unusual cross-coupling of the emitters __ Circuit Design by Jim Hagerman, Nokia Mobile Phones, San Diego, CA

2 transistors form high-precision, ac-mains ZCD -  7-Jun-07 EDN Design Ideas:  A simple two-transistor circuit can accurately detect the zero crossing of the ac mains voltage __ Circuit Design by Djessas Zoheir, Constantine, Algeria

2N2222 40 Meter CW/DSB Tranceiver -  in spring of 1998, NorCal sponsored a contest to design and build a project using no ICs  and 22 or fewer 2N2222s as the active semiconductor devices.  I thought this was a really intriguing idea, so I set about to design my version __ Designed by Monty Northrup

2-Step Power Conversion: Portable Power for the Future -  Design Solutions 8 Design Notes__ Linear Technology/Analog Devices

2-Transistor Amplifier -  it has been interesting analyzing these radios.  You have to give the Japanese credit for even making a radio that can drive a speaker with only 2 transistors! Basically, the first transistor (Q1) performs double-duty.  it first acts as an RF amplifier, with some of the signal being fed back to the antenna coil to provide some regeneration for better selectivity and sensitivity __ Designed by schematic and circuit description were provided Ronald Rissel

2-Transistor FM Transmitter -  While there are a plethora of similar 2-transistor schematics available, this one is above average.  A major improvement over the little 1-transistor circuit that we've discussed previously this transmitter__ copy of geocities.com/tomzi.geo page

3 Transistor Amplifier -  This electronic circuit design shows a simple two transistor amplifier with feedback.  it offers a reasonably high impedance while providing a low output impedance.  __  

300v Peak to Peak Signal Generator -  This circuit converts a square wave signal to a +-150 volt output signal with fast 100nS rise and fall times. . . Circuit by David Johnson P.E.-June, 2000

3-transistor current source covers wide range -  05/31/14  EDN Design Ideas:  This Design idea is a two-wire current regulator that strikes a good balance between performance and parts count.  Employing three transistors, three resistors, and one LED, it achieves good regulation (better than 1% over most of the voltage range) , lower operating voltage (1.2V typical) , and better tempco (0.07%/K) than other circuits of similar complexity.  it is designed to operate in a range of currents from tens of milliamperes to several amps.  it does not use any hard to find parts; for example: an LM10 can be used to make an even higher performance circuit, but this IC is not multi-sourced and is likely to be discontinued.   __ Circuit Design by Einar Abell0

4 Small Transistor Alarm Circuits -  Battery-Powered Alarm Circuits:  This is a selection of simple self-contained transistor based alarm circuits - complete with photographs.  They are designed around the Complementary Latch.  All may be triggered by both normally-open and normally-closed switches.  They have a very low standby current - and are ideal for battery operation.  __ Designed by Ron J.

4 Transistor Tracking Transmitter -  Schematic and parts list only, no circuit description included.   __ Designed by Tony van Roon  VA3AVR

4 Transistor Transmitter -  This circuit provides an FM modulated signal with an output power of around 500mW.  The input Mic preamp is built around a couple of 2N3904 transistors, audio gain limited by the 5k preset.  The oscillator is a colpits stage, frequency of oscillation governed by the tank circuit made from two 5pF capacitors and the inductor __ Designed by Paul K Sherby

40nVpp Noise, 0.05uV/C Drift, Chopped FET Amplifier -  For very high precision low frequency applications, chopping the dc input signal to create an ac signal and then synchronously demodulating the signal to restore the dc value eliminates all static dc errors of the components used.  This is a high gain (Av=1001) example with excellent low offset voltage and drift with temperature __ Linear Technology/Analog Devices App Note, Mar 16th 2010

4-transistor H-bridge -  An interesting 4-transistor H-bridge variant; this is cheap and easy to build, and best of all is "smokeless" (i.  e.  , no combination of inputs can cause the bridge to self-destruct).   __ Designed by Steve Bolt

4W FM Transmitter -  This is a small but quite powerful FM transmitter having three RF stages incorporating an audio preamplifier for better modulation.  t has an output power of 4 Watts and works off 12-18 VDC which makes it easily portable.  it is the ideal project for the beginner __ Designed by © smart kit electronics

6-transistor H-bridge -  This issix transistor "Tilden style" H-bridge; while not as old asoriginal "basic H-bridge, " this goes "way back, " and is basis for many BEAM driver circuits __ Contact Bruce Robinson

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Transistors:  #'s - C    D - I     J - O     P - S     T - Z


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