This differential amplifier, found in a 1964 Electronic Design, has a gain of 30. The setting can be applied to modern equivalent transistors.
In this charger, the charging current is basically limited by the LEDs. The transformer is a low...
This circuit is from the Analog Devices component datasheet. In it we have the way to obtain a low...
Found in a Philips documentation from the 90s, this circuit uses transistors from that time....