Circuits & Schematics Texas Instruments

1. Painlessly convert Hz to 4-20mA current loop
   Stephen Woodward
   Circuits Supply Texas Instruments LM2917-N
   The iconic LM2917 tackles frequency-to-current conversion with (very) few externals. Almost exactly 50 years ago in June 1976, to be precise National Semiconductor introduced the LM29x7 series, offering deceptively simple monolithic solutions to a ...
   Jul 16, 2026
2. Solid state airflow sensor with linear 4-20mA output
   Stephen Woodward
   Circuits Analogue Design Measurement Texas Instruments LM7905 TLV2197
   A self-heated Darlington transistor pair makes a simple, sensitive, and sturdy airflow sensor. But first an annoying non-linearity needs unbending. If you take a self-heated transistor in a TO-92 package and force it to hold a constant temperature ...
   Jul 14, 2026

3. Tachometer frequency to 4-20mA loop current converter
   Jayapal Ramalingam
   Circuits Measurement Texas Instruments LM2907
   Converting frequency signals to loop current signals creates an economical result for process industry applications. Process industry applications commonly employ multiple motors. Their speeds are monitored by tachometers using magnetic pickups ...
   Jul 8, 2026
4. Position sensor gets linear 4 to 20mA current source output
   Stephen Woodward
   Circuits Measurement Texas Instruments SN74HC4066 TLV197-Q1 TLV9051
   A linearized output is a useful elaboration of a capacitive sensor design. But what if the circuit is located a significant distance from the control electronics? Recently, Design Ideas included a circuit ( Ref. 1 ) that comprised a simple analog ...
   Jul 8, 2026
5. Capacitive position sensor with linearized output
   Stephen Woodward
   Circuits Measurement Texas Instruments SN74HC4066 TLV9051
   An only slightly less simple followup circuit also ratios sensor capacitance to a reference capacitor to measure micrometers this time linearly. A few weeks ago, Design Ideas published a simple circuit of mine that provides an analog interface to ...
   Jun 25, 2026
6. 4mA-20mA to 0mA-20mA converter's current mirror drives grounded load
   Stephen Woodward
   Circuits Analogue Design Interfaces Texas Instruments TLV197-Q1 TLV431
   The ubiquity of the 4 to 20 mA current loop in analog process monitoring and control creates possibilities for peculiar designs of circuits for unusual accessory functions. Figure 1 shows an example. It does precision conversion of 4-20 mA to 0-20 ...
   Jun 15, 2026
7. Zener test circuit serves as DC source
   John Jardine
   Circuits Measurement Supply Texas Instruments SN74HC132
   This Design Idea describes a versatile test circuit for zener diodes after yet another misread zener diode had infiltrated the ranks of 1N4148 diodes assembled on a pc board. As a bonus, the circuit can serve as a moderate-voltage, power-limited ...
   Jun 8, 2026
8. Triply simply sequence supply voltages
   Stephen Woodward
   Circuits Supply Texas Instruments CD40106B
   This circuit design for power supply on/off sequencing uses Schmidt triggers for triple-positive-rail timing purposes. Recent design ideas have explored the utility of timed power supply ON/OFF sequencing and provided circuit designs to implement ...
   Jun 4, 2026
9. ΔVbe thermometer is switchable between °C and °F
   Stephen Woodward
   Circuits Measurement Texas Instruments CD4073B
   Ordinary bipolar junction transistors can sometimes be precision sensors. When you think of precision components, you usually don’t (and probably shouldn’t) think of general-purpose bipolar junction transistors. Are GP BJTs cheap and ...
   May 14, 2026
10. Over-temperature micro-power alarm
    David A. Johnson
    Circuits Measurement Digital Texas Instruments CD4013B
    The circuit is powered for years by a single 3 volt lithium battery. It sounds an alarm when the temperature exceeds a certain point. With some minor changes the circuit could also be configured for an under temperature (freeze) alarm. The circuit ...
    May 14, 2026

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