This adjustable power supply circuit, designed for laboratory use with a range of 0-50V and 0-4A, features the classic TL081 op-amp design commonly found in electrical and electronic circuit textbooks. The output stage employs 4 BD249 transistors along with a laboratory power supply transformer. With a 50V AC output, it can deliver a robust current of 4 amps. Alternatively, utilizing a 2X25VAC transformer is a more efficient approach, especially when integrated with a relay bypass circuit for regulated power supplies.
It’s worth noting that ready-made modules with integrated voltmeters and ammeters (utilizing ICL7107) are readily available in the market. These modules are designed for use in regulated power supply circuits and come with built-in features. In the same circuit’s PCB layout, additional components, including a 3.3k potency adjustment, have been incorporated to enhance the circuit’s functionality.
Users of the laboratory-type power supply circuit neglected to employ an insulator for the power control transistors. In this design, where voltmeter and ammeter components are absent, transistor T4 (BD140) is connected to the heatsink, although it is not mandatory. This setup integrates the collectors of BD239 and BD249 transistors, eliminating any insulator between the coolant and the transistors. Consequently, the entire coolant voltage runs through it. If the power supply is housed in a metal case, direct contact with the chassis can lead to breakdown. It emphasizes the importance of both heat conduction and the use of insulators in such setups.
- Wide common-mode (up to VCC+) and differential voltage range
- Low input bias and offset current
- Output short-circuit protection
- High input impedance JFET input stage
- Internal frequency compensation
- Latch-up free operation
- High slew rate: 16 V/µs (typ).