Circuits & Schematics - 5

Awhile back I published a simple design idea for a thermal airspeed sensor based on a self-heated Darlington transistor pair ( Ref. 1 ). See Figure 1. Figure 1. Older design idea with self-heated Darlington thermal airflow sensor. In the circuit, ...

To control their brightness, LEDs need a constant current; this can be done with a resistor placed in series with the LED string. Both the LED-string voltage and the supply voltage can vary, so a dedicated LED driver is a must to guarantee the ...

Intrinsically capacitive transducers and other high-impedance signal sources usually require ac coupling and a buffer amplifier to condition the signal for further processing. Buffers take many forms, but most of them compromise signal quality ...

This Design Idea describes a new class of logic gates, which we have named resistor-FET-logic, aka “RFL.” How do we know it is new? While FET switches are common today, we have been unable to find a similar resistor-FET-logic. Further, ...

A classic analog application is the full-wave precision rectifier (absolute value) function. Many variations exist on this theme, each with its own supposed (often rather minor and sometimes downright dubious) advantages compared to competing ...

While choosing an op-amp buffer, some sources of negative supply were considered, because the buffer op-amp had to provide true zero voltage on its output. In reality, a typical rail-to-rail output op-amp isn’t capable of this, it can ...

Capacitance sensors measure a wide variety of physical quantities, such as position, acceleration, pressure and fluid level. The capacitance changes are often much smaller than stray capacitances, especially if the sensor is remotely placed. I ...

Figure 1 shows a chopped amplifier that requires only 5.5 µA supply current. Offset Voltage is 5 µV, with 0.05 µV/ C drift. A gain exceeding 10 8 affords high accuracy, even at large closed-loop gains. Figure 1. 0.05 µV/ C ...

The traditional analog function generator with its customary triple-threat ensemble of square, triangle, and sine waveform outputs is a familiar tool on electronics lab benches. It’s also a classical design exercise. Generally, the square and ...

The bandpass filter circuit shown in Figure 1 features an electronically controlled Q. Q for a bandpass filter is defined as the ratio of the 3 dB pass bandwidth to the stop bandwidth at some specified attenuation. The center frequency of the ...