Problems to Chapter 1
1.Define shortly the following terms:
• voltage gain;
• current gain;
• power gain;
• inverting and non-inverting amplifier;
• input impedance;
• output impedance;
• loading effect;
• cascade connection of two amplifiers;
• power supply efficiency;
• power gain, expressed in dB;
• voltage gain, expressed in dB;
• ideal voltage amplifier;
• ideal current amplifier;
• frequency response;
• half power frequency (-3dB frequency) and frequency bandwidth;
• midband, low-frequency and high frequency region of frequency response of an amplifier;
• wideband and narrow band amplifier;
• rise time;
• ringing.
• over shoot;
• differential amplifier;
• differential and common-mode signal;
• common-mode rejection ratio (CMRR).
2. A certain noninverting amplifier has a voltage gain magnitude of 50. The input voltage is
vi(t)=0.1sin(2000πt) (a) Find a expression for the output voltage vo(t). (b) Repeat Part (a) for
an inverting amplifier. (Exercise 1.1)
3. A source with internal voltage Vs = 1mV rms and internal resistance of Rs = 1MΩ is
connected to the input terminal of an amplifier having an open-circuit voltage gain of
Avo=104, and input resistance of Ri=2MΩ, and an output resistance of Ro= 2Ω. The load
resistance is RL = 2Ω. Find the voltage gains Avs=Vo/Vs and Av = Vo/Vi . Also, find the current
gain and power gain. (Example 1.1)
4. Consider the cascade connection of two amplifiers shown in Figure 1.20. Find the current
gain, voltage gain, and power gain of each stage and for the overall cascade connection.
(Example 1.2)
Ro2
Ro1
+
vi1
500Ω
Ri1
1MΩ
-
200vi1
Amplifier 1
+
100Ω
vi2
-
Ri2
100vi2
1500Ω
+
RL
100Ω
vo2
-
Amplifier 2
Figure 1.20.
5. Determine the overall simplified model for the cascaded amplifier in Figure 1.20 (Example
1.2).
6. A certain amplifier is supplied with 1.5A from 15V supply. The output signal power is
2.5W and the input signal power is 0.5W. Find the power dissipated in the amplifier and the
efficiency. (Exercise 1.6)
7. An amplifier has an input resistance of 2kΩ, an output resistance of 100Ω, and an opencircuit voltage gain of Avo = 2000. If this amplifier is operated with a load of RL = 300Ω,
find the power gain in decibels and the voltage gain Av=vo/vi in decibels. (Exercise 1.7)
8. A certain amplifier is modeled by the voltage- amplifier model shown in Figure 1.26. Find
the current amplifier model. (Example 1.5)
Ro
100Ω
Ri
1kΩ
100vi
Figure 1.26
9. The input voltage of a certain amplifier is
vi (t ) = 0.1cos 2000πt − 300
and the output voltage is
vo (t ) = 10 cos 2000πt + 150
Find the complex voltage gain of the amplifier and express the magnitude of the gain in
decibels. (Example 1.8)
(
)
(
)
10. Find the minimum CMRR for the electrocardiograph amplifier if the differential gain is
1000, the desired differential input signal is 1mV peak, the common - mode input signal is a
100V peak 60Hz sine wave, and it is desired that the output contain a peak common - mode
contribution that is 1% or less of the peak output caused by the differential signal. (Example
1.9)