Re: Bidirectional amplifier, DC measurements.

Rahul Srivastava

Just keep in mind 2N2222 metal and PN2222 plastic have different lead configration.
Its C B E  L to R for metal where as it is E B C     L to R for plastic when viewed from front. Leads going down.
Rahul VU3WJM

eternalesquire wrote:

Here are my AC and DC measurements for the Q3 amplifier circuit.  I
had used a scope to measure rather than my voltmeter, so measurements
are eyeballed.

With R set to 12V from an external power supply.
Anode of diode is 9 V
Cathode of diode/collector of Q3 = 8 V
Base = 3 V
Emitter = 3 V (probably a tad less due to BE voltage drop)

From BFO through an attenuator, I am applying 10.7 Mhz signal of
5mV pp seen by scope injected at junction of input capacitors

25 mV pp same frequency seen at junction of output capacitors.

I get no amplification whatever when power is removed or reversed,
which is what we want.

Except for the AC gain, this appears to be a properly DC biased small
signal transistor amplifier.

On the other sets of amplifier circuits, I see 50 mV pp at junction of
output capacitors.

Could it be that I am using the wrong techniques to view the signal
with my scope, rather than there being a bug in the circuit?  I'm
halfway tempted to try putting this circuit in LTSpice as a sanity check.

Scratching my head in confusion,

The Eternal Squire

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