Multistage Transistor Amplifiers

Question 1

The term “cascade” refers to what?

Answer 1

The term “cascade” refers to how the output of one amplifier is applied to the input of another.

Question 2

When several amplifiers are connected together, each individual amplifier is called a ______.

Answer 2

When several amplifiers are connected together, each individual amplifier is called a STAGE.

Question 3

The purpose of cascade amplifiers is to _______.

Answer 3

The purpose of cascade amplifiers is to increase gain.

Question 4

What formula is used to find the overall gain of a cascade amplifier?

Answer 4

Av (total) = Av1 x Av2 x Av3

Av (total) = 10 x 10 x 10 = 1000

Question 5

There are four methods used to couple one amplifier to another. Which one is showed below?

Answer 5

Resistance - Capacitance (RC) coupling

• the most common method of coupling one stage to the next and uses inexpensive components.
• The output signal is developed across collector load resistor (Rc1) and is coupled across the coupling capacitor (Cc2) into the base of the next stage.
• The coupling capacitor passes AC signals and blocks DC signals.
• The disadvantage of RC coupled amplifiers is the low frequency response. At low frequencies, the reactance of the coupling capacitor becomes too large, reducing the input and output signals.
• RC coupling is used in almost all types of cascade amplifiers except low frequency amplifiers.

Question 6

There are four methods used to couple one amplifier to another. Which one is showed below?

Answer 6

Inductance - Capacitance (LC) coupled amplifiers

• The coupling capacitors pass AC signals and block DC signals as in RC coupled amplifiers.
• L1 and L2 have very low resistances to DC. Vcc is applied almost directly to Q1 and Q2 collectors.
• L1 and L2 AC resistance depends on the frequency.
• The advantage of high AC resistance is that very little AC power is wasted in the inductor. All the AC power is coupled to the next stage.
• The disadvantage is the inductors are more expensive than resistors and their reactance drops off at lower frequencies.

Question 7

There are four methods used to couple one amplifier to another. Which one is showed below?

Answer 7

Transformer Coupling

• coupling capacitors are not used between stages. A transformer is used instead.
• In High Frequency amplifiers, a capacitor is added in parallel with the transformer windings. This enhances the amount of signal that is coupled from stage to stage.
• The output of each stage is connected to the primary windings of T1 and T2.
• The inputs to the next stage are taken from the secondary windings of T1 and T2.
• Transformer coupling is used in radios and TVs. It is the principle behind tuning in a radio station or TV channel. Transformer coupling is normally used at RF frequencies for radio and TV.

Question 8

Which type of coupling is used in this cascade amplifier circuit?

Answer 8

direct

Question 10

Which type of coupling does not use coupling capacitors but still uses a reactive component?

RC
LC
transformer
direct

Answer 10

transformer

Question 11

Which type of coupling is used in this cascade amplifier circuit?

RC
LC
direct
transformer

Answer 11

RC

Question 12

What is the total gain of this cascaded amplifier?

49
90
900
9000

Answer 12

9000

Question 13

What is the total gain of this cascaded amplifier?

10
20
990
1000

Answer 13

990

Question 14

In cascaded amplifier circuits, individual transistor circuits are called _______.

stages
amplifiers
coupled amplifiers
cascade amplifier circuits

Answer 14

Stages

Question 15

Which type of coupling is the most common method used?

RC
LC
transformer
direct

Answer 15

RC

Question 16

In a circuit that connects the output of one amplifier to the input of another, the configuration is called _______.

impedance matching
coupling
cascade
stage

Answer 16

Cascade

Question 17

Which type of coupling does not use reactive components?

RC
LC
transformer
direct

Answer 17

Direct

Question 18

Which type of coupling is used in this cascade amplifier circuit?

RC
LC
direct
transformer

Answer 18

LC