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Sunday, 29 May 2011

How much current?????

I've been building the linear amplifier as part of the ongoing HF tranciever project in RadCom. This specific article was in March 2011. Here's the schematic of the amp:


Now, the actual build in the article uses a TPV3100 dual transistor (it's 2 devices in one package - I think). Being somewhat clueless about transistor characteristics and equivalents; I've ended up using a pair of 2SC1971's.

I've built the amp here:



And the bias is currently set to minimum which is 0.748 volts. With just the bias connected the current draw is about 70mA. If I then add power to either transistor (not both) via T2 the current draw increases to 1.85A. This seems rather excessive.

What I don't know is a) if the transistors I have used are suitable for this application and b) what sort of standing current I should expect.

Nothing is getting excessively hot, and no smoke has come forth, so it's not a total disaster (yet).

All this has been possible with the assistance of my second in command:



Can anyone help?

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