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Last Updated:  Wednesday June 02, 2021 01:44:28 PM

Circuits Designed by Dave Johnson, P.E.

RS-232 Serial Interface Status Indicator CircuitI designed this circuit many years ago and have used it several times since.  It uses a single logic IC to indicate the TXD and RXD line activity of a typical RS-232 serial data communications link.  The thresholds are set at plus 3 volts and minus 3 volts.  Two dual color LEDs are used as indicator lights . . . Hobby Circuit designed by Dave Johnson P.E.-December, 2007

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

Rearranged reference helps ADC measure its own supply voltage -  28-Apr-05 EDN-Design Ideas Clever topology allows self-measurement of power supply rail__ Circuit Design by Björn Starmark and Orville Buenaventura, Maxim Integrated Products Inc, Sunnyvale, CA, and Sören Käck, Audioväxlar, Sweden

Recover the leakage energy of a flyback transformer -  04/18/13  EDN-Design Ideas This design can recover the leakage energy of a flyback transformer and minimize over-voltage stress to the switching device.  __ Circuit Design by Todor Arsenov

Reduce EMI by sweeping a power supply's frequency -  27-May-04 EDN-Design Ideas Switching power supplies can be notorious noise generators.  You should prevent this noise, which is conducted, radiated, or both, from returning to the input source, where it can potentially wreak havoc on other devices operating from the same input power.  The goal of an EMI(electromagnetic-interference] filter is to block this noise and provide a low-impedance path back to the noise source__ Circuit Design by John Betten, Texas Instruments, Dallas, TX

Reduce voltage-reference output noise by half -  3-Feb-05 EDN-Design Ideas Reducing low-frequency(1/f] noise generated by an IC voltage reference can prove difficult.  In theory, adding a lowpass filter to a reference's output reduces noise.  In practice, a lowpass RC filter for suppression of noise frequencies below 10 Hz requires large values of series resistance and shunt capacitance__ Circuit Design by Alfredo H Saab and Steve Logan, Maxim Integrated Products Inc, Sunnyvale, CA

Reference stabilizes exponential current -  10/25/01 EDN-Design Ideas In an antilog converter, the difference between the base voltages of two transistors sets the ratio of their collector currents  The use of matched transistors balances the first-order temperature coefficient but leaves a temperature-dependent gain term, q/kT.  Classic antilog circuits use a thermistor in the drive circuitry to correct this temperature dependency__ Circuit Design by Tom Napier, North Wales, PA

Regulated 12V Supply -  This circuit above uses a 13 volt zener diode, D2 which provides the voltage regulation.  Aprroximately 0.7 Volts are dropped across the transistors b-e junction, leaving a higher current 12.3 Volt output supply.  This circuit can supply loads of up to 500 mA.  This circuit is also known as an amplified zener circuit __ Designed by Mick Devine

Regulated High-Voltage Supply for Valve Amplifiers -  How to modify a surplus PC power supply to produce a 700V or 400V high-voltage rail.___ SiliconChip

Regulated Linear power supply with LM317-1.5, 3, 4.5, 5, 6 & 9 Volt -  Normally begin to learn about electronics power supply from the battery, for example, 9 volts, 1.5 volts, 6 volts etc.  But there are disadvantage that when using battery power is discharged.  I need to buy a new one.  Consume more.  We should the dc power supply have a choice of AC voltage.  Which it must […] __ Designed by Antonio Rodrigues

Regulator Can Source & Sink Current -  12/07/95  EDN-Design Ideas Although a positive supply regulator usually acts solely as a current source, some applications require both sourcing and sinking.  For these applications, Linear Technology’s LT1118 family of low-dropout regulators can source and sink as much as 800 and 4__ Circuit Design by Bill Schweber Linear Technology Corp, Milpitas, CA.

Regulator Excels in Noise & Line Rejection -  Certain electronic circuits require extremely low-noise power supplies and this circuit provIdeas very good quality power output.  __ Circuit Design by Walt Jung, Analog Devices Inc, Norwood, MA

Regulator Generates as Many as Four Voltages -  08/03/95 EDN-Design Ideas The inexpensive switching regulator in Fig 1 provIdeas as many as four voltages using a single quad comparator.  The circuit can implement two positive regulated supplies and two semiregulated negative supplies that use a charge-pump technique.  Fig 1's circuit, which costs $4.48 in moderate volumes, shows three of the four possible output voltages, ±9V and 150V.  You can add a 150V supply using the same charge-pump techniques as the 9V supply.  Output current of the +9V supply is nominally 10 mA.   __ Circuit Design by D Hayden, Hayden Electronics Design, San Diego, CA

Regulator Generates Both 3.3V & 5V Outputs from 3.3V or 5V to Run Computers & RS-232 -  DN71 Design Notes___ Linear Technology/Analog Devices

Regulator Generates Sub-Bandgap Voltage -  01/02/97 EDN-Design Ideas 100-mA regulator that uses a dual linear-regulator IC to produce output voltages below1.25V from2.9 to5.5V input-voltage range__ Circuit Design by Ronald Young and Luong Huynh, Maxim Integrated Products, Sunnyvale, CA

Regulator has One Active Part -  03/16/95 EDN-Design Ideas The regulator of unusual simplicity (ROUS) in Fig 1 derives a low-voltage, low-current output from rectified 115 to 270V ac.  Pass transistor Q1 is the regulator's only active component.   __ Circuit Design by Kennan C Herrick, ESI Electronics Corp San Francisco, CA

Regulator IC forms convenient overvoltage Detector -  09/28/00 EDN-Design Ideas Figure 1 shows a simple, stand-alone overvoltage detector.  The intent of the circuit is to monitor a voltage, VMONITOR, and set the output, VOUT, high when the monitored voltage exceeds a preset threshold.  The minimum allowable threshold for this circuit is 1.25V.  The operation of the circuit revolves around the TLV431 shunt regulator.  This IC is based on the popular TL431 shunt regulator.  The difference is that the TLV431's internal reference is 1.25V, as opposed to 2.5V for the TL431.  When the voltage at the control input is less than 1.25V, the regulator's cathode current is essentially zero__ Circuit Design by Robert Bell

Regulator Makes Dual Tracking Reference -  11/07/96 EDN-Design Ideas You can use the venerable 723 voltage regulator in new and unusual ways.  For example, you can modify its topology as in Figure 1 to yield a low-component-count, dual-polarity tracking voltage reference.  The 723, a long-time standard in power-supply design, is a flexible IC that includes a temperature-compensated voltage reference, an error amplifier,__ Circuit Design by James Mears, National Semiconductor, Tacoma, WA

Regulator Monitors its input voltage -  09/12/97 EDN-Design Ideas Two- and three-cell portable systems, such as medical sensors, often monitor their battery input to obtain an early warning of a loss of battery voltage.  Typically, this warning is a digital signal that a comparator generates and then sends to the microcontroller.  The circuit in Figure 1 presets one side of a dual linear regulator to generate 2.84V at 100 mA.  The other side operates open loop, as a comparator, to generate the low-battery warning.  Both sIdeas are capable of delivering 100- mA output current.  Resistors R1 and R2 determine the low-battery threshold, according to__ Circuit Design by Larry Suppan and Luong Huynh, Maxim Integrated Products, Sunnyvale, CA

Regulator provides ±12V -  10/23/97 EDN-Design Ideas Simple circuit can provide ±12V from a5V input using only one switching-regulator IC and a few off-the-shelf__ Circuit Design by Musiri Shrivathsan, National Semiconductor Corp, Santa Clara, CA

RS-232 Serial Interface Status Indicator Circuit -  I designed this circuit many years ago and have used it several times since.  It uses a single logic IC to indicate the TXD and RXD line activity of a typical RS-232 serial data communications link.  The thresholds are set at plus 3 volts and minus 3 volts.  Two dual color LEDs are used as indicator lights . . . Hobby Circuit designed by Dave Johnson P.E.-December, 2007


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