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Discriminator Circuits
Discriminators:  #'s - D     E - Z

 

Last Updated: November 30, 2017 07:39 AM

Circuits Designed by Dave Johnson, P.E.

Indicate DC Current Flow The circuit below is a simple way to indicate when DC current is flowing through a wire.  The circuit is designed so it will turn on a LED indicator light, whenever the voltage drop across a shunt resistor exceeds about 0.1volts.  The value of the resist . . . Hobby Circuit designed by David A. Johnson P.E.-October, 2005

Indicates Battery Charge Current This circuit turns on a LED whenever it detects at least 25ma of battery charge current . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

Indicator for Acceptable VoltageI have used this circuit many times in custom test fixtures where a simple go-no go indication was needed.  The circuit can also be used to adjust a particular voltage be within specific high or low limits.  The three LEDs will indicate if the voltage is . . . Hobby Circuit designed by David A. Johnson P.E.-February, 2002

Precision AC Peak DetectorThis unique circuit uses a very inexpensive voltage comparator to form a peak detector.  The DC voltage produced tracks the positive peak of the input signal.  It works from about ten millivolts to about 10 volts peak to peak.  The maximum frequency is about. . . Circuit by Dave Johnson P.E.-February, 2002

Thermostat for 12v Cooling FanThis circuit will turn on a 12v DC powered cooling fan when the air temperature reaches a certain high temperature and will keep the fan turned on until the temperature drops below a second lower level.  Both the high and low temperatures are both adjustable . . . Hobby Circuit designed by David A. Johnson P.E.-February, 2011

Version 4 of a DC Current IndicatorThe circuit below uses some common components to turn on an LED whenever DC current above a certain level is detected.  The circuit uses a very popular LM393 dual voltage comparator from National Semiconductor and a common 1N4148 signal diode.  The diode . . . Hobby Circuit designed by Dave Johnson P.E.-October, 2005


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

Electronic fuse emulates fast- or slow-blow fuses -  11/09/00 EDN-Design Ideas The electronic-fuse circuit in Figure 1 combines the properties of a current transducer and a solid-state relay to disconnect low power at preset levels.   Using this circuit lets.   PDF contains multiple circuits, scroll to find the one of interest__ Circuit Design by John A Hasse, Colorado State University, Fort Collins, CO

Expanded-scale indicator revisited -  08/08/02 EDN-Design Ideas The visualization aid that a previous Design Ideas describes allows only the expansion of the upper end of the scale(Reference 1].  But what can you do if, according to your project requirements, you need to expand the middle region of the scale? Figure 1a illustrates the challenge.  A voltmeter comprises a 100-µA dc meter and a series resistor__ Circuit Design by Abel Raynus, Armatron International Inc, Melrose, MA

Fast comparators find theIR niche in linear application -  09/11/98  EDN Technical Article: Comparators don’t “just compare” in the same way that op amps don’t “just amplify.  ” A collection of application circuits demonstrates just how flexible and useful a high-speed comparator can be.  __ Circuit Design by Jim Williams, EDN's most revered contributor, passed away in June 2011 after a stroke.  He was 63.

Frequency comparator draws 8 mA -  03/03/97  EDN-Design Ideas The circuit in Figure 1includes all the necessary components to build a simple, low-power frequency comparator.  The circuit centers around the operation of IC1, which integrates an amplifier, a comparator, and a voltage reference.__ Circuit Design by Dalius Baranauskas, Semiconductor Physics Institute, Vilnius, Lithuania

Indicate DC Current Flow -  The circuit below is a simple way to indicate when DC current is flowing through a wire.  The circuit is designed so it will turn on a LED indicator light, whenever the voltage drop across a shunt resistor exceeds about 0.1volts.  The value of the resist . . . Hobby Circuit designed by David A. Johnson P.E.-October, 2005

Indicates Battery Charge Current -  This circuit turns on a LED whenever it detects at least 25ma of battery charge current . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

Indicator for Acceptable Voltage -  I have used this circuit many times in custom test fixtures where a simple go-no go indication was needed.  The circuit can also be used to adjust a particular voltage be within specific high or low limits.  The three LEDs will indicate if the voltage is . . . Hobby Circuit designed by David A. Johnson P.E.-February, 2002

Light Sensor with Hysteresis -  It is quite a simple circuit but rather more effective than the one using the 741.   It uses a simple comparator LM311 as the mater piece.   This comparator is powered from a +12V DC supply and does not require negative supply to work efficiently. __ Designed by Frank Rivard

Low Power Comparator with <10uV Hysteresis -  The opamp is used as a precision comparator that drives an NPN transistor to form a logic-level output.  Controlled positive feedback into a trim pin makes precision microvolt hysteresis control practical.  __ Linear Technology/Analog Devices App Note, Jun 21st 2011

Low Voltage Alarm -  NE555 Low Voltage Battery Disconnect Circuit __ Designed by Aaron Cake

Microvolt Compararator with TTL Output -  Amplifiers can easily be used as comparators although somewhat slower than dedicated circuits.  Very accurate comparison threshold is provided by the low offset of the amplifier.  Feedback to one of the offset adjust pins adds hysteresis to prevent oscillations when the inputs are close to each other.  __ Linear Technology/Analog Devices App Note, Jun 21, 2011

Microvolt Comparator with Hysteresis -  Very low offset, 20uV typical, can produce extremely accurate comparator functions.  Small input voltages can produce oscillations without hysteresis.  Here hysteresis is added to a Vos trim pin to as to not degrade the input precision.  __ Linear Technology/Analog Devices App Note, Jun 21, 2011

Missing Pulse Detector Basic -  This circuit is a one-shot that is continually retriggered by incoming pulses.   __ Designed by Tony van Roon  VA3AVR

Missing-codes tester checks 16-bit ADC in 7 sec -  06/10/99 EDN-Design Ideas As the resolution of ADCs increases from 12 to 16 bits and higher, the difficulty in testing the"nomissing-codes"specification grows proportionately.  To fully guarantee no missing codes for a 16-bit ADC requires testing all 2 16-1 possible output__ Circuit Design by Mark A Shill, Burr-Brown Corp, Tucson, AZ

One-Shot Provides Frequency Discrimination -  05/01/03  EDN-Design Ideas You use a frequency discriminator to compare one signal frequency with another one.  A functional feature, retriggering, of a monostable, one-shot 74xx123 multivibrator can yield frequency discrimination.  Figure 1 shows a frequency discriminator that determines the relation of input-pulse frequency to a reference frequency__ Circuit Design by Victor Aksenenka, CSRI Elektropribor, St Petersburg, Russia

Pilot Light Flame Detector with Low-Battery Lockout using a Type R Thermocouple -  The LTC1541 combine a micropower amplifier, comparator and bandgap reference in an 8-pin package.  The part operates from a single 2.5V to 12.6V or dual ±1.25V to ±6.3V supply with a typical supply current of 5µA.  Both the op amp and comparator feature a common mode input voltage range that extends from the negative supply __ Linear Technology/Analog Devices App Note, Apr 8th 2010

Precision AC Peak Detector -  This unique circuit uses a very inexpensive voltage comparator to form a peak detector.  The DC voltage produced tracks the positive peak of the input signal.  It works from about ten millivolts to about 10 volts peak to peak.  The maximum frequency is about. . . Circuit by Dave Johnson P.E.-February, 2002

Pulse Generator Has 0ns to 10ns Width, 520ps Transitions -  It is sometimes desirable to produce extremely short width pulses in response to an input trigger.  Such a predictable, programmable short time interval generator has broad use in fast pulse circuitry, particularly in sampling applications.  This circuit, built around a quad high speed comparator and a fast gate, has a settable __ Linear Technology/Analog Devices App Note, Mar 25th 2010

Rail-to-Rail 1MHz Pulse Width Modulator -  In applications where a high frequency variable PWM generator is needed, the LT1715 provides a small and simple solution, as shown in the circuit of Figure 10.  The top comparator, U1A, acts as a ramp generator.  Biasing resistors R1 and R2 and a 7:1 positive feedback ratio through R3 set the positive input to approximately 2.5V±250mV.  __ Linear Technology/Analog Devices App Note, Mar 31, 2010

Schottky Diodes Improve Comparator’s Transient Response -  21-Jan-10 EDN-Design Ideas Two Schottky barrier diodes clamp error voltages, cut output glitches__ Circuit Design by Marián Stofka, Slovak University of Technology, Bratislava, Slovakia

Synchronized Window Comparator Eliminates Error -  05/11/95 EDN-Design Ideas Precision A/D converters need a window comparator.  The window comparator in Fig 1a is synchronized to the clock signal.  This synchronization eliminates errors that could arise when the input signal crosses the high or low threshold(Fig 1b]unsynchronized to clock.  In operation, comparator IC1A sets flip-flop IC2__ Circuit Design by Sergey Velichko, Consultant, Bosie, ID

Thermostat for 12v Cooling Fan -  This circuit will turn on a 12v DC powered cooling fan when the air temperature reaches a certain high temperature and will keep the fan turned on until the temperature drops below a second lower level.  Both the high and low temperatures are both adjustable . . . Hobby Circuit designed by David A. Johnson P.E.-February, 2011

Two buttons provide safe start -  07/06/00 EDN-Design Ideas The circuit in Figure 1 provIdeas a safety interlock that checks the actuation of two pushbuttons before enabling a relay.  When you push both buttons, the circuit actuates the relay.  At that point, you can release one of the switches without the relay'__ Circuit Design by   Vincent Himpe, Alcatel Microelectronics, Desselgem, Belgium

Version 4 of a DC Current Indicator -  The circuit below uses some common components to turn on an LED whenever DC current above a certain level is detected.  The circuit uses a very popular LM393 dual voltage comparator from National Semiconductor and a common 1N4148 signal diode.  The diode . . . Hobby Circuit designed by Dave Johnson P.E.-October, 2005

Voltage Comaparator & Q Multiplier make a stable Sine Wave Oscillator (in PDF format) -  It is a known fact that sinusoidal oscillators must rely on the action of some amplitudelimiting mechanism in order to achieve good frequency and amplitude stabilities.  Likewise, accurate loop-gain control and high-Q tuned circuits are required for the attainment of low-distortion output levels.   __ Designed by Ramon Vargas

Voltage Comparator -  This experiment only requires a single operational amplifier.  The model 1458 and 353 are both "dual" op-amp units, with two complete amplifier circuits housed in the same 8-pin DIP package.  I recommend that __ Designed by Tony R. Kuphaldt

Voltage comparator forms pulse Demodulator -  11/19/98 EDN-Design Ideas NOTE :  File contain several designs.  Scroll to find this one.  To process low-level ultrasound or radio-range pulses, you need a signal-conditioning amplifier followed by a pulse demodulator to translate the signals to dc pulses.  Traditionally, you would use a diode-demodulator configuration (for example, the circuit in Figure 1a) with one stage of a single-supply op amp.  The circuit in Figure 1b does the same job but uses a voltage comparator instead of a diode demodulator.  __ Circuit Design by Abel Raynus, Armatron International, Melrose, MA  

Voltage Comparator Switch -  This circuit will provide an indication whenever the input voltage differs from two defined limits, V1 and V2.  The supply voltage, Vcc must be higher than the highest input voltage by at least 2 volts.  One application here is to monitor a 12V car battery __ Designed by Andy Collison

Voltage Comparator with Complementary Outputs -  Circuit Ideas for Designers App Note___ Advanced Linear Devices, Inc


Discriminators:  #'s - D     E - Z


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