AC voltage probe (CB8185E)

This circuit for voltages up to about 20 V was found in a 90s Popular Electronics. The LED can be of any type or color.

Up to 30 MHz Oscillator (FET) (CB13144E)
The circuit shown in the figure can generate signals of good intensity up to a frequency of 30...
Biofeedback Thermometer (CB24401E)
This circuit was found in February 1976, Radio Electronics magazine. The circuit is quite...
150 mA LDO with Texas Instruments TPS780 (CB12548E)
The LDO series (Low Dropout) TPS80 from Texas Instruments (www.ti.com) can provide output voltages...