Circuits & Schematics Oscillators

Noise in electrical circuits is typically the enemy, and any self-respecting circuit should output as little noise as possible. Nevertheless, there are cases where a well-characterized source of noise with no other signal is entirely the desired ...

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 ...

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 ...

In Part 1 ( Ref. 1 ) of this article, we briefly looked at the Wien bridge oscillator before homing in on the bi-quad filter as our best candidate for an oscillator capable of giving 0.0001%/ 120 dB distortion, and showed its full circuit. Treating ...

Over the years, the Design Ideas (DI) column has featured many interesting oscillators, but none that I can recall was specifically designed to produce a really clean sine wave. Putting that omission together with the need to rebuild my old ...

I recently purchased a new oscilloscope for home use. It’s a 250 MHz scope, but I was curious what the actual 3 dB frequency was as most scopes have a bit more upper end margin than their published rating. The signal generators I have either ...

In the classic configuration and most variants of the astable 555 multivibrator circuit, the timing characteristics are based on the charging and discharging of a capacitor. However, it can be argued that since the exponential voltage of a ...

A previous Design Idea “Gated 555 astable hits the ground running” ( Ref. 1 ) 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 ...

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 can conveniently be used ...

Second test circuit I looked at several types of AGC circuits (strictly, Automatic Level Control). JFETs are the usual starting-point but are inherently non-linear and need to be surrounded by lots of stuff to limit the signal voltage across them ...