Multi-functional Packaged Antennas for Next-Generation Wireless Applications

1
Basic amplifier concepts
Voltage gain reducing by 1/?2 times indicates
that power will be reduced by half, at the half
power frequencies.
2
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.
3
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.
4
Basic amplifier concepts
5
Basic amplifier concepts
6
Basic amplifier concepts
1. Measure the common mode gain Acm
2. Measure the differential gain Ad
3. Compute the CMRR 20 log ?Ad/Acm
7

• 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 ? 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 K?,
  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 K?
• P1.63 CMRR 60 dB

Answer -20 dB and CMRR 114 dB