Circuits & Schematics

Let’s imagine that you need to add a power switch to something that’s battery-powered but processor-free; perhaps it must also be waterproof and thus membrane-sealed. Or perhaps you just want to use a shiny modern push-button rather ...

The CD4011 CMOS NAND gate has a typical input current of 10 pA at room temperature. You can charge a capacitor connected to the gate input with currents on the order of hundreds of picoamperes and neglect the influence of the gate-input current on ...

The exposure tester in this Design Idea measures the on time of a light source, whether an LED, an incandescent lamp, a halogen lamp, or another source. It can be made with an ordinary stopwatch and a few simple components (figures 1 and 2). An ...

It is common practice to power a MOSFET with a comparator and with an unregulated voltage and to power the comparator driving it from a regulated one (Figure 1). Many loads are insensitive to driving voltage, so it would be a waste of money and ...

Recently I published a simple platinum resistance temperature detector (PRTD) design idea ( Reference 1 ) that was largely inspired by a deviously clever earlier DI by Nick Cornford ( Reference 2 ). Remarkable and consistently constructive critical ...

A high-side current-sense amplifier, IC 1 , offers a simple method of combining low-speed clocks or other signals with dc power in cables between subsystems (Figure 1). Designed for monitoring charge and discharge current in secondary batteries, IC ...

Frequent contributor Nick Cornford recently published a delightfully clever design idea ( Reference 1 ) using a platinum RTD calibrated to output a 1 mV/ C signal that’s perfect for direct readout via a standard DMM I thought Nick’s ...

Way back in 1986, famed analog innovator Jim Williams, in “Designs for High Performance Voltage-to-Frequency Converters” ( Reference 1 ) published his “King Kong” 100 MHz VFC. I have never seen its equal. Certainly Figure ...

Before shipping moving-coil meters, manufacturers may short-circuit the meters' terminals with a length of wire, which provides effective electromagnetic damping and results in better immunity to external mechanical vibration and shocks that ...

There are several applications at home or industry for long delay timers (ON or OFF delay). Time delays on the order of seconds can be generated using 555 timer circuits, provided the timing capacitor values do not exceed the limit specified by 555 ...