The simplest in-circuit transistor tester

This is the simplest in circuit transistor tester. It uses two ammeters to measure the transistor gain. It is kinda like the heathkit IT-18 one but uses 2 meters instead of one. I plan on using relays for the polarity switch instead of a 5PDT Rotary switch. It uses a LM317 regulator for providing a very low voltage(around 1.25v). This will prevent turning on anything on and interfering with the gain measurements. The capacitor is to remove oscillations. I used two 8 cent 10nF capacitors in series to make 5nF. All [P] switches are all part of the polarity relays. I need a 4pdt relay and a spdt relay used to provide the 5pdt switch.

Circuit diagram

How do I measure the gain?

The gain is simply


Where hFE is your gain, Ic is your collector current and Ib is your base current I did the math with the transistor in the circuit diagram and got around 195.

Electronics Workbench Model of 2N4403
Power Supply

The collector meter is 50mA and base meter is 100uA

A video will soon come when the parts come in the mail

Published by Justin Roeder

I am an electronics engineer and computer programmer that has autism. I learned by myself

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