Testing the Amplifier


The goal of this experiment is to find out whether the amplifier being used really works.  A generator is used to generate a voltage instead of the synthesizer.   This voltage is read on the voltmeter.  Then the generator is attatched to the amplifier along with 4 attenuators (20 dBm).  The voltage from this setup is read, and since it is known how attenuators work in series, the voltage from the amplifier can be measured.

The given signal is 100.65 mV.  Each attenuator should decrease this signal by a factor of 10, making the final sigal .010065 mV.  The voltmeter cannot read such a small signal, so the amplifier is set with a gain of 50,000.  This should increase the signal to 503.25 mV.  This is the theoretical value that the voltmeter would read if the attenuators and amplifier were perfect. 

The attenuators were calibrated.  A generator with a signal of 100 mV was plugged into a voltmeter, and the voltage was read.  Then an attenuator was added between the generator and  voltmeter, and this decreased the signal by a factor of ten, which is what an attenuator is supposed to do. Each attenuator was tested in this way, and each gave acceptable ouput.

In reality, the voltmeter reads .289 Volts.  But one cannot forget that the 50 ohm resistor on the voltmeter changes the signal by a factor of two.  So the signal is really (2)(.289 V), which is .578 V, or 578 mV.  587 mV is close enough to the theoretical value of 503.25 mV to know that the amplifier does work.

Back to Paper

Back to Outline