Single Stage Transistor Amplifiers MCQs with Explanations

The gain in decibels (dB) is a way to express the ratio of two power levels on a logarithmic scale. The formula to convert power gain to dB gain is: dB gain = 10 * log10 (Power Gain) In this question, the power gain is 100. So, dB gain = 10 * log10 (100) Since 100 is 10 squared (10^2), log10 (100) is 2. Therefore, dB gain = 10 * 2 = 20 dB. So, a power gain of 100 corresponds to a dB gain of 20 dB .

Input impedance is like the resistance the amplifier presents to the signal source. We generally want a high input impedance for a transistor amplifier. Think of it this way: A high input impedance means the amplifier doesn't load down the signal source too much. If the input impedance is low , it would draw a significant amount of current from the source, reducing the signal strength and potentially distorting it. Therefore, a high input impedance allows the amplifier to receive the signal with minimal disturbance to the source.

A Common Emitter (CE) amplifier is widely used for voltage amplification. The question asks about the phase difference between the input signal voltage and the voltage developed across the collector load resistor (RC) , not the collector terminal voltage. When the input signal voltage increases, the base current ( I B ) increases. This causes the collector current ( I C ) to increase because the collector current is directly proportional to the base current in the transistor's active region. The voltage across the collector load resistor is given by V RC = I C × R C . Since the collector current increases, the voltage drop across RC also increases. Similarly, when the input signal decreases, the collector current and the voltage across RC also decrease. Thus, the input signal voltage and the voltage across RC rise and fall together. They are therefore in phase , resulting in a phase difference of 0° . Why the Other Options are Incorrect: 180°: This phase difference exists between the input signal and the collector terminal (output) voltage , not between the input signal and the voltage across RC . The collector voltage is given by V C = V CC − V RC , so it decreases when V RC increases. 270°: A phase difference of 270° does not occur in the normal operation of a single-stage CE amplifier and has no significance in this context. 90°: A 90° phase shift is characteristic of purely reactive circuits containing inductors or capacitors. Since RC is a resistor, it does not introduce a 90° phase shift. Key Point to Remember: Voltage across RC is in phase (0°) with the input signal because both increase and decrease together. Collector terminal (output) voltage is 180° out of phase with the input signal because it is equal to V CC − I C R C . Therefore, the phase difference between the voltage across the collector load resistor (RC) and the input signal voltage is 0° . Therefore, Option D is the correct answer.

Grounded emitter is the correct answer to “A CE amplifier is also called ___________ circuit”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

Collector has reverse bias is the correct answer to “A transistor amplifier has high output impedance because ___________”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

RC is the correct answer to “In a single stage transistor amplifier, RC and RL represent collector resistance and load resistance respectively. The transistor sees a d.c. load of ___________”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

RC + RE is the correct answer to “A single stage transistor amplifier with collector load RC and emitter resistance RE has a d.c. load of ___________”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

More than is the correct answer to “The d.c. load of a transistor amplifier is generally ___________ that of a a.c. load”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

Low is the correct answer to “If a transistor amplifier feeds a load of low resistance (e.g. speaker), then voltage gain will be ___________”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

RC || RL is the correct answer to “If RC and RL represent the collector resistance and load resistance respectively in a single stage transistor amplifier, then a.c. load is”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

CE is the correct answer to “For highest power gain, one would use ___________ configuration”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

Electrolytic is the correct answer to “In transistor amplifiers, we generally use ___________ capacitors.”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

Coupling is the correct answer to “The input capacitor in an amplifier is the ___________ capacitor”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

β is the correct answer to “In a CE amplifier, voltage gain = ___________ $$ \times \frac{{{{\text{R}}_{{\text{AC}}}}}}{{{{\text{R}}_{{\text{in}}}}}}$$”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

One transistor is the correct answer to “A single stage transistor amplifier contains ___________ and associated circuitry”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

More than is the correct answer to “The slope of a.c. load line is ___________ that of d.c. load line”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

Input impedance is very high is the correct answer to “CC configuration is used for impedance matching because its ___________”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

5 kΩ is the correct answer to “If a transistor amplifier draws 2mA when input voltage is 10 V, then its input impedance is ___________”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

Less than is the correct answer to “The value of collector load RC in a transistor amplifier is ___________ the output impedance of the transistor.”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

Avoid voltage gain drop is the correct answer to “The purpose of emitter capacitor (i.e. capacitor across RE) is to ___________”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

RC is the correct answer to “A single stage transistor amplifier with no load sees an a.c. load of”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

Couple or bypass a.c. component is the correct answer to “The purpose of capacitors in a transistor amplifier is to ___________”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

Pass a.c. and block d.c. is the correct answer to “The purpose of a coupling capacitor in a transistor amplifier is to ___________”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

Biasing conditions will change is the correct answer to “If the input capacitor of a transistor amplifier is short-circuited, then”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

180° is the correct answer to “The phase difference between the output and input voltages of a CE amplifier is ___________”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

Moderate is the correct answer to “The ratio of output impedance of a CE amplifier is ___________”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

Open is the correct answer to “In the d.c. equivalent circuit of a transistor amplifier, the capacitors are considered ___________”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

Short is the correct answer to “In the a.c. equivalent circuit of a transistor amplifier, the capacitors are considered ___________”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

Set up operating point is the correct answer to “The purpose of d.c. conditions in a transistor is to ___________”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

Collector supply VCC is the correct answer to “The output power of a transistor amplifier is more than the input power because the additional power is supplied by ___________”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

Operating point is the correct answer to “The point of intersection of d.c. and a.c. load lines is called ___________”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

A million is the correct answer to “The radio wave picked up by the receiving antenna is amplified about times to have reasonable sound output”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

165 is the correct answer to “If the power and current gains of a transistor amplifier are 16500 and 100 respectively, then voltage gain is”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

10 V is the correct answer to “If the collector supply is 10V, then collector cut off voltage under d.c. conditions is ___________”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.

Thin base is the correct answer to “In order to get more voltage gain from a transistor amplifier, the transistor used should have ___________”. This question is standard in competitive examination syllabi for Single Stage Transistor Amplifiers.