Question

For a transistor amplifier, the voltage gain
(a) is high at high and low frequencies constant in the middle frequency range.
(b) is low at high and low frequencies and constant in the middle frequency range.
(c) remains constant for all frequencies.
(d) is high at high frequencies, low at low frequencies and constant in the middle frequency.

Answer 1

Hint: This question can be solved with the help of the fact which is stated as the increment and decrement of the voltage gain is similar to that of the frequency and the mid-ranges of a transition amplifier gives constant voltage gain with intermediate frequency ranges.

Complete step by step answer:
We will consider the diagram of a transistor which is shown below.
 

As the name suggests, the NPN transistors are the ones which consist of a p-type semiconductor between two N-type semiconductors. But in case of a PNP type transistor, one P-type semiconductor works between two N-type semiconductors. Here, N is used for negative and P is used as positive. In the diagram the arrow shows the direction of the electrons which flows from the input to emit as an output in NPN transistor whereas it flows opposite in case of PNP transistor. The NPN transistor is used more as compared to the PNP transistor. This is due to the fact of the movement of the electrons in the NPN transistor rather than the PNP transistor.
Now, we will study about the frequency and voltage gain in the transistor. The diagram showing the relation between the frequency and the voltage gain is given below.

Clearly, by the diagram we come to know that the voltage gain increases with the increase in the frequency whereas it decreases with the decrease in the frequency. However, it remains constant at mid-frequency ranges.

So, the correct answer is “Option B”.

Additional Information:
Amplifier: By the term amplifier we mean a type of an electronic device, which helps in the increment of the power of the input signals and produces an output signal. Output signal is much greater than the input signal. If we see in our day to day lifestyle then we get to know that electronic devices such as radio, television, guitar and so on come under the category of amplifiers.
Transistor amplifier: By the term of transition amplifier we mean a kind of a laser type transistor which processes the changing between two electronic levels.
Voltage gain: Since, there is need to measure the increase of an amplification, so for that the voltage gain works as a measurement here which basically finds the value of the increment of the amplification from an input signal to the output signal by adding energy converted from some power supply to the signal. It is simply the ratio of the output voltage to the input voltage.
If for example the input signal in a transition amplifier is of 1 Voltage and the output made by it carries 50 Voltage then, the voltage gain here is going to be the ratio of the input signal to the output signal resulting into the voltage gain as 50:1.
Frequency: By the term frequency we mean a regularity of one wave occurred in one second. This is basically measured in terms of Hertz.

Note: The things to be on your finger tips for further questions like this are,
(1) The SI unit of frequency is Hertz which is written as Hz.
(2) The SI unit of Voltage gain is decibel written as dB.
(3) The voltage gain and the frequency both increase and decrease simultaneously while if the frequency is made mid-range then the voltage gain remains constant.
(4) The graph of voltage gain with respect to frequency.