75 years ago, one of the biggest electronics firms of the century got its start in a Palo Alto, California, garage – and it did so with the help of Mickey Mouse...
Articles and news - 6
A 1939 audio oscillator caught Disney's eye - and helped launch HP
More gated 555 astable multivibrators hit the ground running
A previous Design Idea “Gated 555 astable hits the ground running” offered a fix for the problem of the excessively long first pulse that’s generated by traditional topology 555 astable circuits on start up when gated by the RESET pin...
Simple log-scale audio meter
While refurbishing an ageing audio mixer, I decided that the level meters needed special attention...
Gated 555 astable hits the ground running
The classic and versatile 555 finds its way into many low to moderate frequency oscillator applications. Some of these require the ability to selectively gate oscillation on and off on demand and the 555’s RESET pin...
Temperature drift compensation for audio power amplifiers
This article describes a technique to compensate the DC voltage drift in the output of a directly-coupled AB-Class audio power amplifier...
Adding one resistor improves anemometer analog linearity to better than ±0.5%
Awhile back I published a simple design idea for a thermal airspeed sensor based on a self-heated Darlington transistor pair. In the circuit, Q1 plays the role of self-heated sensor. Its VBE tempco converts temperature into voltage which is then offset and scaled by A2 to a 5 V span...
Proper function linearizes a hot transistor anemometer with less than 0.2% error
A recent Design Idea presents a circuit to measure an airflow rate up to 2000 fpm using two transistors in a Darlington configuration. One transistor works as a self-heated thermal sensor and the other one compensates for ambient temperature variations. The circuit is smart and simple; however, the output voltage depends on the input flow rate in a very nonlinear fashion...
A simple, accurate, and efficient charge pump voltage inverter for $1 (in singles)
Keeping op-amp outputs “live” at and below zero volts, generating symmetrical output signals, and processing bipolar analog inputs, are all examples of design situations where a few milliamps of negative voltage rail can be a necessity...
Squashed triangles: sines, but with teeth? Part 2
Second test circuit I looked at several types of AGC circuits (strictly, Automatic Level Control)...
Squashed triangles: sines, but with teeth? Part 1
A while ago, I needed (or wanted) a pocket-sized audio sine-wave generator: simple, stable, repeatable, single-gang control pot, 9 V battery-powered. A “squashed tri-wave” approach looked appropriate...
