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

Last Updated: October 18, 2017 05:04 AM

Circuits Designed by Dave Johnson, P.E. :

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

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 . . . Hobby Circuit designed by Dave Johnson P.E.-March, 2002

Sink to Source Universal DC Converter -  As illustrated below, many control systems use an open collector transistor to turn something on.  Perhaps it is a LED light, a relay or a small motor.  However there are others systems which require a common ground connection instead of a common V+ supply connection. . . Circuit by David A. Johnson P.E.-March, 2011

Solid State Touch Activated Switch -  it does not get any easier if you want a solid state switch that is activated by the touch of a finger.  Two small metal pins route voltage through the finger skin to a MOSFET switch.  The circuit is great for situations where a membrane type mechanical switch . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2000

Capacitance Proximity Switch
Draws very low power - Ideal for battery-powered applications
6 Models Available - Call 806-368-7747


Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

Paralleling FETs -  When I built the GW3UEP 630m transmitter, I made one small modification by adding a second FET in parallel with the first. Normally when dealing with RF devices (tubes, RF transistors) in non-switching modes, adding a second device in parallel with the first, always guarantees a significant increase in output power. This is not the case with FETs when parallelled in switch-mode amplifiers. __ Designed by VE7SL - Steve

P-channel power-MOSFET driver uses unity-gain op Amp -  21-Jan-10 EDN Design Ideas:  Drive a power MOSFET to 100V dc with this signal-conditioning circuit __ Circuit Design by Suded Emmanuel, Emmanuel's Controls, Auckland, NZ

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

Power MOSFET is Core of Regulated-DC Electronic Load -  03/17/05 EDN Design Ideas:  Designers use electronic dc loads for testing power supplies and sources, such as solar arrays or batteries, but commercial ones are often expensive.  By using a power MOSFET in its linear region, you can build your own (Figure 1).  __ Circuit Design by Ausias Garrigós and José M Blanes, University Miguel Hernández, Electronic Technology Division, Elche, Spain

Power Resistor Varies In Value -  07/28/11  EDN Design Ideas:  Under controlled conditions, a MOSFET can function as a variable power resistor.  Testing power supplies or discharging batteries usually requires a constant-current load.  Sometimes, however, you must study the behavior when the load is a resistor.  Using a high-power potentiometer is an expensive approach that might not be worth the cost.   __ Circuit Design by Bogdan Raducanu, Bucharest, Romania

Produce Current from Positive or Negative High-Voltage Supplies -  05/26/11  EDN Design Ideas:  A simple modification lets you use an N-channel MOSFET in both applications.   __ Circuit Design by Kurt Nell, Sankt Pölten, Austria

Protect MOSFETs In Heavy-Duty Inductive Switched-Modes -  02/03/11  EDN Design Ideas:  Measure peak currents and use ac coupling to prevent FET burnout.  The MOSFET power switch is commonly the most vulnerable part of a new switched-mode high-power circuit.  One threat for this device is exceeding the value of the maximum allowed pulse current.  You cannot exceed this limit, even for pulse durations as short as 10 nsec.  You could still thermally damage the MOSFET with a high duty cycle even when the drain-to-source current has a value between the peak and the dc ratings. __ Circuit Design by Marián Štofka, Slovak University of Technology, Bratislava, Slovakia

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 . . . Hobby Circuit designed by Dave Johnson P.E.-March, 2002

Provide ISFET-sensor bias -  10-Jun-04 EDN Design Ideas:  iSFETs (ion-sensitive field-effect transistors] are useful for measuring the acidity of fluids.  Accurate measurements require that the iSFET's bias conditions (iD and VDS] be held constant while the gate is exposed to the fluid under __ Circuit Design by Brian Harrington, Analog Devices, Wilmington, MA

Pushbutton replaces rotary switch -  26-Oct-00 EDN Design Ideas:  The problem of setting any one of four modes of aµC-operated process has a straightforward solution  Have the µC check the states of some 4 bits of aµC.    __ Circuit Design by Abel Raynus, Armatron International Inc, Melrose, MA

Push-Pull Complementary Power MOSFET Driver -  Circuit ideas for Designers App Note__ Advanced Linear Devices, Inc

Quasi-Complementary Amplifier -  Several Circuits, be sure to scroll down.  First up is quasi-complementary amplifier.  Unusual to see in 2014, but great fodder for learning what goes on in a PA.  After making, debugging and analyzing these circuits, I felt humbled about how little I consider AC signal phase in addition to the easier concepts of amplitude and frequency during my AC signal analysis. __ Contact Vasily Ivanenko

Recommended Handling Procdures for Microwave transistor & MMIC Chips 1/92  -  App Note  Doc #929__ California Eastern Laboratories

Reduce negative-voltage stresses on control IC -  04/18/02  EDN Design Ideas:  in a synchronous, buck switching power supply, the two FETS and the output inductor meet at the phase node (Figure 1).  The phase node often connects directly to the control IC .  The voltage on this node swings from the input voltage  __ Circuit Design by Michael Day, Texas Instruments Inc, Dallas, TX

Relay Toggle using a MOSFET  & Push Button -  This circuit is similar to the one above, but uses a N channel mosfet such as iRF530, 540, 640, etc.  in place of the NPN transistor.  Smaller mosfets could be used, but I don't know the part numbers.  I tested the circuit with a iRF640, iRFZ44, iRFZ34 and REP50N06.   The circuit has the same three advantages, it requires only a few parts, always comes up with the relay deactivated, and doesn't need any switch debouncing. __ Designed by Bill Bowden

Replace ORing Diodes with MOSFETs to Reduce Heat & Save Space -  DN363 Design Notes__ Linear Technology/Analog Devices

Reverse Polarity Protector -  A series diode is often used as a means of protecting equipment from accidental power supply reversal, particularly in battery-powered equipment.  Due to forward voltage losses, this is sometimes impractical.  One solution is to use an enhancement mode P-channel power Mosfet (Q1) in series with the positive supply rail.  A device with low drain-source “on”__ 

RS-232c Level Converter using Transistors -  There're many, who built the Easy Programmer or C-52 EvaluationBoard, asking for the RS232C level converter chip, DS275.  Many have changedto MAX232 instead, because of not available in his home.  Here is anothersimple and cheap circuit using small signal transistor providing TTL toRS232C level converter __ Designed by Wichit Sirichote

Select Vo by using EPAD Transistor & Resistor Ratios -  Circuit ideas for Designers App Note__ Advanced Linear Devices, Inc

Series-connected MOSFETs increase voltage & power handling -  EDN Design Ideas:  01/05/2015    A constant-current charger for a high-energy capacitor bank uses multiple MOSFETs to increase voltage and power-handling capabilities __ Circuit Design by Ilija Uzelac & Ron Reiserer

Simple  Transistor Type & Lead Identifier -  A bipolar junction transistor (BJT) has three regions, of which the emitter and the collector are made of the same type of semiconductor (‘n’ for npn and ‘p’ for pnp) but...__ Electronics Projects for You

Simple Circuit 3 Transistor Audio Amp 50 Milliwatt -  Here is a little audio Amplifier similar to what you might find in a small transistor radio __ Designed by Bill Bowden

Simple Circuit Detects Current Pulse -  01/06/94 EDN Design Ideas:  The pulse detector provide as a visible indication of positive and negative current pulses.  The pulses amplitudes can vary from20 to150 mA.  The pulses durations can range from10 to40 msec, and their repetition rate can span40 to180 pulses/minute __ Circuit Design by Richard McGillivray, Grey Bruce Regional Health Centre, Owen Sound, Ontario, Canada

Simple Circuit FM Transmitter with a Single Transistor -  MinI FM transmitters take place as one of the standard circuit types in an amateur electronics fan's beginning steps.  When done right, they provide very clear wireless sound transmission through an ordinary FM radio over a remarkable distance.  I'veseen lots of designs through the years, some of them were so simple, some of them were powerful, some of them were hard to build etc.   __ Designed by Kamran Ahmed-UK

Simple Circuit Inverter -  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

Simple Circuit Lets You Characterize JFETs -  04/06/12  EDN Design Ideas:  Measure the pinch-off voltage VP and zero-bias drain current iDSS to select matched pairs of JFETs.   __ Circuit Design by John Fattaruso

Simple Circuit Transistor Organ -  This simple circuit can provide hours of enjoyment as you learn tunes, play duets or just make some really weird sounds by pushing all the buttons at once.  You have probably seen this circuit before, it is fairly common.  I have seen it in several __ Designed by Aaron Cake

Simple Circuit two transistor lights LEDs -  9-Apr-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 transistor, which operate as a high-gain amplifier __ Circuit Design by Barry A Tigner, Michigan State University, East Lansing, MI

Simple Circuit VCOM adjustment uses any logic-supply voltage -  09/30/04 EDN Design Ideas:  All TFT [thin-film-transistor] LCD panels require at least one appropriately tuned VCOM signal to provide a reference point for the panel’s backplane.  The exact value of VCOM  varies   Page includes several designs.  Scroll to find this one __ Circuit Design by Peter Khairolomour and Alan Li, Analog Devices, San Jose, CA

Simple Mosfet Switch -  Constructing a MOSFET switch is one of the basic level electronics projects and could be useful for beginners to get a hang of the various FET transistors.  The aim of this project is to make control a heavy duty DC load by constructing a simple switch.  MOSFET transistors are capable of handling a large voltage__ 

Single Transistor Provides Short-Circuit Protection -  16-Oct-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 the short circuit through the inductor and the catch diode.  Regardless of current-limit protection in the IC , when a short circuit exists in the load, extremely high cu __ Circuit Design by Keith Szolusha, Linear Technology Corp, Milpitas, CA

Single transistor sequences multiple supplies -  08/08/02 EDN Design Ideas:  Many DSP chips, microprocessors, FPGAs, and ASIC s require multiple power supplies that must deliver different voltages in a specific start-up sequence.  Out-of-sequence voltages can cause excessive input current, logic errors, or even device failure.  To sequence different supplies, a common approach is to regulate a lower voltage from a higher voltage using a linear regulator __ Circuit Design by David Chen, Linear Technology Corp, Milpitas, CA

Single-MOSFETs gate & Modulate -  EDN Design Ideas:  07/27/2015    The humble discrete MOSFET shows its versatility in This design idea      __ Circuit Design by Umar Shami

Sink to Source Universal DC Converter -  As illustrated below, many control systems use an open collector transistor to turn something on.  Perhaps it is a LED light, a relay or a small motor.  However there are othersystems which require a common ground connection instead of a common V+ supply connection. . . Circuit by David A. Johnson P.E.-March, 2011

Solid State Tesla Coil Chapter 7 -  in this chapter, we deal with the design of the Tesla coil driver.  We will discuss several components or subsystems, including the power supply, the controller, the gate driver and inverter, the fast fuse, and the current sense resistors __ Designed by Solid State Tesla Coil Dr. Gary L. Johnson

Solid State Touch Activated Switch -  it does not get any easier if you want a solid state switch that is activated by the touch of a finger.  Two small metal pins route voltage through the finger skin to a MOSFET switch.  The circuit is great for situations where a membrane type mechanical switch . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2000

Stable Multivibrator Transistor -  I will introduce the a-stable multivibrator circuit which used two transistors.  The a-stable multivibrator is the circuit which repeats the high level (H) condition and the low level (L) condition alternately.  ‚hin case of the transistor type, the voltage (Vcc) of the power supply __ Designed by Seiichi Inoue

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

 


Imagineering Ezine    Discover Solar Energy Dave Johnson & Associates Faraday Touch Switches



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