This circuit generates various types of sounds and can be used as a toy. The circuit is from Radio Electronics from January 1983. The amplifier can be replaced with a more modern type.
Found in a 1969’s EDN, this circuit provides 4.5 V with a 100mA current for digital logic. The...
We find this circuit in a 1980s Linear Technology documentation. The circuit can be implemented on the...
Found in Elektor Electronics from the 90s, this circuit can generate signals from 1 kHz to 9 MHz,...