Download Multi-functional Packaged Antennas for Next

Basic amplifier concepts
Voltage gain reducing by 1/2
times indicates that power will
be reduced by half, at the half
power frequencies.
1
Basic amplifier concepts
However, often the signal contain a “common” voltage applied to both terminals that also affects the
output signal. This is not desirable, and a good amplifier needs to minimize such effects.
2
Basic amplifier concepts
The patient has a common mode input due to the parasitic capacitances. The ECG machine must be able to ignore
the common mode signal and not amplify it.
3
Basic amplifier concepts
4
Basic amplifier concepts
5
Basic amplifier concepts
1. Measure the common mode gain Acm
2. Measure the differential gain Ad
3. Compute the CMRR = 20 log Ad/Acm
6
Problems
P1.17: An FM radio receiver has an input resistance of 75 Ohm. The input signal provided by a distant
transmitter is 5 µV rms, and the receiver supplies 5 V rms to an 8 Ω loudspeaker. Calculate the
power gain of the receiver.
P1.33: An amplifier has a voltage gain of 30 dB, and a current gain of 70 dB. What is the power gain in dB?
If the input resistance is 100 KΩ, what is the load resistance?
P1.63: A differential amplifier has vo (t) = A1v1(t) – A2v2(t), If A1 = 1000, and A2 = 999, determine the CMRR.
Answers:
P1.17: 9.375 x 1E12
P1.33: GdB = 50, RL = 1 KΩ
P1.63: CMRR = 60 dB
Answer: -20 dB and CMRR = 114 dB
7