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

Last Updated: October 24, 2017 02:55 PM

Circuits Designed by Dave Johnson, P.E. :

JFET High Impedance Buffers -  I have used these circuits many times.  They are great when you need a low gain AC signal amplifier with a very high input impedance.  it is good to beyond 50MHz. . . Circuit by David A. Johnson P.E.-July, 2006

N-Ch & P-Ch Transistor Form Push-Pull Driver -  This circuit can produce high speed output signals with fast rise and full times.  The unique change pump action allows the voltage of the upper P-ch device to range from millivolts to hundreds of volts.  The output current is only limited by the rating of. . . Circuit by David A. Johnson P.E.-June, 2000

NPN/PNP Transistor Tester -  I designed this circuit about 30 years ago and still use it from time to time.  it is powered from a 3v battery.  it makes a tone when the transistor tests good.  it can be used to determine device type (NPN or PNP) and the base, collector or emitter transist . . . Hobby Circuit designed by David A. Johnson P.E.-June, 2000

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JBOT - an SSB linear amplifier made from Just a Bunch of Transistors -  JBOT stands for Just a Bunch of Transistors.  it is a simple, stable and easy to build 5 watts linear amplifier build out of a bunch of ordinary low power NPN transistors.__ 

JFET cascode boosts current-source performance -  05/11/06 EDN Design Ideas:  A constant-current source minimizes the reference circuit's sensitivity to supply-voltage fluctuations and extends the voltage reference's operating voltage beyond its 5.5V maximum rating __ Circuit Design by Clayton B Grantham, Tucson, AZ

JFET High Impedance Buffers -  I have used these circuits many times.  They are great when you need a low gain AC signal amplifier with a very high input impedance.  it is good to beyond 50MHz. . . Circuit by David A. Johnson P.E.-July, 2006

JFET-based DC/DC converter operates from 300-mV supply -  5/25/06  EDN-Design Ideas:      You use a JFET’s self-biasing characteristics to build a DC/DC converter that operates from power sources such as solar cells, thermopiles, and single-stage fuel cells, all of which  deliver less than 600 mVYPDF has several circuits, you will need to scroll to find this one __ Circuit Design by Jim Williams, Linear Technology Corp, Milpitas, CA

JFETs offer LC oscillators with few components -  20-Jan-05 EDN Design Ideas:  By using JFETs in unusual configurations, you can design simple, high-frequency LC oscillators with few passive components.  The structure for implementing the amplifier stage comprises a JFET transistor that you configure as a common drain (Figure 1).  When the JFET transistor works in the saturation zone, the drain current, iD, is  where iDSS is the maximum saturation current and VP is the __ Circuit Design by Herminio Martínez, Joan Domingo, Juan Gámiz, and Antoni Grau, Technical University of Catalonia, Barcelona, Spain

Low Level High Accuracy Bipolar Input Differential to Single-Ended Signal Conversion for 24-Bit A/D Single Supply Differential to Single-Ended Conversion Amplifies Low Level Bipolar Signals & Maintains the LTC2400’s High Accuracy -  Design Solutions 5 Design Notes __ Linear Technology/Analog Devices

Low-Cost MOSFET Quashes Power Resistor -  06/09/94 EDN Design Ideas:  At power-on, off-line power supplies use a resistor to provide start-up current for the PWM IC , current that is necessary to start driving the power switch.  After a few periods, an auxiliary winding delivers a sufficient voltage to power the IC .  Unfortunately, the start-up resistor dissipates heat and __ Circuit Design by Christophe Basso , European Synchrotron Radiation Facility, Grenoble, France

Low-cost Transistorised Intercom -  The circuit described here uses three easily available transistors only.  Even a beginner can easily assemble it on a piece of veroboard.  The circuit comprises a 3-stage resistor- capacitor coupled amplifier.  When ring button S2 is pressed, the amplifier circuit formed around transistors T1 and T2 gets converted into an asymmetrical astable multivib-rator generating ring signals.  These ring signals are amplified by transistor T3 to drive the speaker of earpiece.__ 

Matched Pair EPAD MOSFET Array with a Single Supply -  Circuit ideas for Designers App Note__ Advanced Linear Devices, Inc

Matched Pair EPAD MOSFET with Dual Supplies -  Circuit ideas for Designers App Note__ Advanced Linear Devices, Inc

Micro Spy with FETs -  Circuit and notes only, no circuit description given.   __ Designed by Tony van Roon  VA3AVR

Microcontroller, JFET form low-cost, two-digit millivoltmeter -  06/22/06 EDN Design Ideas:  Software subroutines replace hardware A/D converter __ Circuit Design by Noureddine Benabadji, University of Sciences and Technology, Oran, Algeria

Micropower High-Side MOSFET Drivers -  AN53 Linear Technology This App Note describes the operation of high-side Nchannel MOSFET switch drivers designed specifically for operation in battery-powered equipment, such as notebook and palmtop computers and portable medical instruments.  A selection__ Linear Technology/Analog Devices

Monitoring AC heater currents -  This simple current monitor helped me in prototyping Mammoth, which had 12V * 12A heaters in output stage.  So I had to make sure that all heaters are on.  This 4-channel device (only 2 channels shown) uses DiY current transformers, 30mm ferrite pots with 2-section bobbin.  One half of bobbin is filled with 0.3mm wire (secondary) ; primary is 3 turns of heater wire __ Contact klausmobile @ yahoo.Com

More on two transistor -  05/16/02 EDN Design Ideas:  in a recently published Design idea, Jim Hagerman proposes a two-transistor circuit that claims to replace the LTC4300 hot-swappable, two-wire LTC4300 bus buffer ("Two-transistor circuit replaces IC , " EDN, Feb 7, 2002, pg 104].  I feel compelled to point out that the LTC4300 offers numerous advantages over this circuit for both buffering and hot-swapping the i2C bus __ Circuit Design by Todd Nelson, Product Marketing Manager, Mixed Signal Business Unit, Linear Technology Corp

MOSFET based H-Bridge controller for DC Motors -  To turn on any of the MOSFETs properly in your circuit, the gate voltage has to be significantly higher than the source voltage.  For the lower position devices Q2 and Q4, the sources are grounded to 0V therefore they can easily turn on into "saturation" by applying a gate voltage of a few volts above ground.__ 

MOSFET Beats Murphy's Law -  12/22/94 EDN Design Ideas:  Consider it Murphy's Law: You buy two 15V supplies or one ±15V dual supply to power some op amps.  Then, when the last QA inspector or first customer flips the switch, the power supply hangs up.  This hang-up occurs because the positive supply yanks its output to positive.  The negative supply reads this output as a reverse polarity before it has a chance to start up.  So, the supply's negative regulator gives up.   __ Circuit Design by Phil Harvey, Technology Integration Inc, Bedford, MA

MOSFET Current Sensing -  Method of mirror current sensing a MOSFET __ Designed by Richard Torrens

MOSFET enhances low current measurements using Moving coil meter -  09/15/05 EDN Design Ideas:  Venerable mechanical meter can measure ultralow currents, with some help __ Circuit Design by Stefan Strózecki, Institute of Telecommunications ATR, Kaliskiego, Poland

MOSFET enhances Voltage Regulator's Overcurrent Protection -  3-Mar-05 EDN Design Ideas:  The classic LM317 adjustable-output linear voltage regulator offers a relatively high, if package-dependent, current-handling capability.  in addition, the LM317 features current limiting and thermal-overload protection.  With the addition of a few components, you can enhance an LM317-based voltage regulator by adding a high-speed short-circuit current limiter (Figure 1)  __ Circuit Design by Herb Hulseman, Eagle Test Systems, Mundelein, IL

MOSFET follower Power Amplifier -  Another contributed project that may be of great interest   __ Designed by Pavel Macura

MOSFET H Bridge -  Schematic only - no circuit desciption included __ Designed by Eugene Blanchard

MOSFET LDO Voltage Regulator -  This circuit has excellent voltage regulation, due to positive feedback through R2 however the circuit must be started up.  This is done by Q4 and Q5.  if the circuit does not need to be started under load, Q4, Q5, and R6 can be deleted.  You must then pl __ Designed by Andrew R. Morris

MOSFET Pair makes Simple Circuit SPDT Switch -  12/09/99 EDN Design Ideas:  ith an n-and p-channel MOSFET, you can easily implement a single-pole double-throw (SPDT) switch to isolate part of a circuit and power it from a secondary supplyPDF has several circuits, scroll for this one.    __ Circuit Design by Howard Chen, Vishay Siliconix, Santa Clara, CA

MOSFET Power Amp -  DiY high power MOSFET amplifier200 Wrms 8 ohms -350 Wrms4 ohms __ Designed by Edwin Paij

MOSFET Power Amp (project 101) -  200W MOSFET Hi-FI Power amplifier   __ Designed by Rod Elliott  ESP

MOSFET prevents battery damage -  5-Feb-09 EDN Design Ideas:  A MOSFET protects reverse-connected batteries from excessive current __ Circuit Design by Santosh Bhandarkar, Wep Peripherals, Mysore, India

MOSFET provides high power at low loss -  EDN Design Ideas:  05/12/2011    Use a MOSFET as a rectifier and reduce voltage drop and thus power consumption __ Circuit Design by Camilo Quintáns Graña and Jorge Marcos Acevedo, Vigo University, Vigo, Spain

MOSFET Quashes Power Resistor -  06/09/94 EDN Design Ideas:  At power-on, off-line power supplies use a resistor to provide start-up current for the PWM IC , current that is necessary to start driving the power switch.  After a few periods, an auxiliary winding delivers a sufficient voltage to power the IC .  Unfortunately, the start-up resistor dissipates heat and __ Circuit Design by Christophe Basso , European Synchrotron Radiation Facility, Grenoble, France

MOSFET Replaces Switch -  01/20/94 EDN Design Ideas:  By using a cheap, readily available MOSFET, you can use a single-pole switch to turn a bipolar power supply on and off without consuming extra power.  in Fig1, the switch simply controls the MOSFET gate, which swit __ Circuit Design by Malcolm Watts, Wellington Polytechnic, Wellington, New Zealand

MOSFET Replaces Switch -  02/03/94 EDN Design Ideas:  By using a cheap, readily available MOSFET, you can use a single-pole switch to turn a bipolar power supply on and off without consuming extra power.  in Fig 1, the switch simply controls the MOSFET gate, which switches on the negative supply.  Resistor R, which can be several __ Circuit Design by Malcolm Watts, Wellington Polytechnic, Wellington, New Zealand

MOSFET serves as Ultrafast Plate Driver -  10/03/02 EDN Design Ideas:  The circuit in Figure 1 provide as a 20-MHz square wave across a set of highly capacitive ion-deflection plates in an experimental instrument.  To get the required deflection, the plate voltage must be 20 to 30V, much higher voltage than conventional logic or driver families can provide __ Circuit Design by Clive Bolton, Bolton Engineering Inc, Melrose, MA

MOSFET shunt regulator substitutes for series regulator -  25-Nov-04 EDN Design Ideas:  You would normally use a series linear regulator or a DC/DC converter to obtain 3V dc from a higher supply.  However, when breadboarding a concept, you may be able to use a shunt regulator, especially if a series regulator of the correct voltage is unavailable.  The MOSFET in Figure 1 can replace a zener diode in a shunt regulator and provide lower output impedance than a zener diode __ Circuit Design by Stuart R Michaels, SRM Consulting

MOSFET switch provides efficient ac/DC conversion -  02/17/00 EDN Design Ideas:  Occasionally, you have access to a transformer for powering a dc circuit, but its output voltage is much higher than that required for the dc voltage.  The full-wave-rectified and filtered output of an ac input voltage V X , is V DC =1.414V X-2V F , where V F is the forward drop in the rectifier (approximately 0.7V).    __ Circuit Design by Spehro Pephany, Trexon Inc, Toronto, ON, Canada

MOSFET Tester -  This testing procedure is for use with a digital multimeter in the diode test-range with a minimum of 3.3  volt over d.  u.  t. (Tony van Roon's diode-under-test).  if your multi-meter is less than that it will not do the test.  Check your meter manual for the specs.   __ Designed by Tony van Roon  VA3AVR

MOSFET UPS Regulator's Output Current -  02/01/96 EDN Design Ideas:  Use a current mirror and a power MOSFET to increase the output-current capability of an IC -voltage regulator.    __ Circuit Design by Robert Buono, Universal Sonics Mahwah, NJ

MOSFET, Inverter 12 volt unit -  A Very Reliable, Efficient and Practical Design.  Do Not ask how to Build this for Power ratings over 1000 watts, That is NOT Practical.   __ Designed by G.L. Chemelec

MOSFET-based Joule Thief steps up voltage -  EDN Design Ideas:  02/23/2015    This Design idea illustrates a novel approach to the Joule Thief circuit __ Circuit Design by Sajjad Haidar

MOSFET-Based Preamplifier for FM Radio Dxing -  FM transmissions can be received within a range of 40 km.  if you are in fringe areas, you may get a very weak signal.  FM DXing refers to hearing distant stations...__ Electronics Projects for You

MOSFET-based, analog calculates square root -  19-Feb-09 EDN Design Ideas:  Square-root-calculating circuits find wide use in instrumentation and measurement systems for such tasks as calculating the rms (root-mean-square) value of an arbitrary waveform, for example.  Hence, designers need an effective analog square-root calculator.  Because manufacturers __ Circuit Design by Abhirup Lahiri, Netaji Subhas Institute of Technology, New Delhi, India;

MOSFETs Reduce Crosstalk Effects On Analog Switches -  02/17/97 EDN Design Ideas:  Some cost-effective analog multiplexer/demultiplexer IC s, such as the CD4053 and CD4066, find frequent use as signal distributors.  These digitally controlled analog switches have low on-resistance.  However, with all channels in the same package, crosstalk can be annoying and unavoidable.  Figure 1 provide as a cost-effective and viable method of solving this problem.  By simply adding some n-channel MOSFETs, such as the 2N7002 or 2N7000, the crosstalk effect becomes negligible.  When the Channel Select signal is high, the CD4053's input pins A, B, and C assume a level of nearly 0V.   __ Circuit Design by Stanley Chen, Global Mixed-Mode Technology, Taipei, Taiwan

N-Ch & P-Ch Transistor Form Push-Pull Driver -  This circuit can produce high speed output signals with fast rise and full times.  The unique change pump action allows the voltage of the upper P-ch device to range from millivolts to hundreds of volts.  The output current is only limited by the rating of. . . Circuit by David A. Johnson P.E.-June, 2000

NPN/PNP Transistor Tester -  I designed this circuit about 30 years ago and still use it from time to time.  it is powered from a 3v battery.  it makes a tone when the transistor tests good.  it can be used to determine device type (NPN or PNP) and the base, collector or emitter transist . . . Hobby Circuit designed by David A. Johnson P.E.-June, 2000

One 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

One Transistor Radio -  Here is a simple circuit for a one transistor Audion type radio powered by a 1.5 V battery.  it employs a set of standard low-impedance headphones with the headphone socket wired so that the two sides are connected in series thus giving an impedance of 64 Ω.  The supply to the circuit also passes through__ 

One-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.  __ 

Op Amps Make Automatic-Oring Power Selector -  08/11/11  EDN Design Ideas:  Replace diodes with FETs to reduce power loss.  Many systems must select among two or more low-voltage dc-input sources, such as an ac adapter, a USB (Universal Serial Bus) port, or an onboard battery, for example.  You can implement this selection using manual switches, but automatic switching is preferable.  You usually want to use the highest-available input voltage to power your system.  You can accomplish this task using a Schottky-diode ORing scheme (Figure 1).  Unfortunately, the forward-voltage drop of a Schottky diode ranges from 300 to 600 mV.  This voltage wastes power, creates heat, and decreases the voltage available to your system.   __ Circuit Design by Bobwicker, Analog Devices, Fort Collins, CO

Op Amps make JFETs repeatable -  05/24/01 EDN Design Ideas:  Because they use practically no bias current (a useful feature in itself) , JFETs also have practically no current noise.  This feature means that you can use JFETs in very-high-resistance circuits and obtain good noisePDF has many circuits, scroll for this one __ Circuit Design by Glen Brisebois, Linear Technology Corp, Milpitas, CA

Optimize Phototransistor Bandwidth -  04/09/98 EDN Design Ideas:  (several circuits included, scroll the find this one) A simple circuit can improve the dynamic performance of a phototransistor for use in low- to medium-speed applications as fast as 100 kbps, such as optical isolation of an RS __ Circuit Design by David Magliocco, CDPI, Scientrier, France

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Please eMail
if you want me to link to and/or post your original design.  Thanks.


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

 


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