Programmable Uni-junction Transistor (PUT) FlasherThis is simple circuit that illustrates the function of the programmable unijunction transistor. It may be quickly wired on a proto-board
PUT Flasher Specifications
- Flash rate: approx 1hZ
- Load current: approx 300uA
- Minimum voltage: approx 4V
PUT Flasher Circuit Schematic
By varying (programming) the gate voltage, the voltage at which the transistor fires varies—in this case, it varies the flash rate.
This cute little device was developed by General Electric about 50years ago. The original GE part numbers were D13K1 and D13K2 (now 2N6027 and 2N6028). The 2N6028 has tighter specifications for more precision applications. On Semiconductor is now the sole manufacturer, but NTE has a relatively expensive equivalent device.
There are many, many applications for this device, but it is mainly useful for triggering thyristors. Other than for thyristor triggering, the ubiquitous 555 timer has taken over.
Proto-board circuit layout
Bill of Materials
- Q1 On Semiconductor 2N6027 (comes only in T0-92 package)
- R1 100K
- R2 10K
- R3 22K
- C1 10uF, 25V aluminum electrolytic
- D1 LED Red, High Brightness
- Battery Standard 9V