Multistage Amplifiers
DEFINITION:
An amplifier with two or more stages arranged in a manner that the output of one serves as the input for the next, while amplifying at each step. It is also called cascade amplifier.
EXPLANATION:
In most of the cases the gain provided by a single stage amplifier stage is insufficient. Consequently two or more amplifier stages are cascaded in order to increase the gain. Several amplifiers can be connected in a cascaded arrangement with the output of one amplifier driving the input of the next. Each amplifier in cascaded arrangement is known as stage. The basic purpose of multistage arrangement is to increase the voltage gain. It is understood that combining amplifiers of various types we can create those characteristics that are necessary to fulfill the specifications of a specific application.
GAIN FOR MULTISTAGE:
The overall gain of a multistage amplifier is the product of the gains of the individual stages (ignoring potential loading effects):
Gain (A) = A1* A2*A3 *A4 *... *An.
Alternately, if the gain of each amplifier stage is expressed in decibels (dB), the total gain is the sum of the gains of the individual stages:
Gain in dB (A) = A1 + A2 + A3 + A4 + ... An BANDWIDTH: The cascading in amplifiers obviously increases the gain. At the same time it also affects the bandwidth of an amplifier. And bandwidth decreases as the number of stages increase.
The way in which the individual stages are coupled together is important. The design of the coupling circuitry must fulfill several requirements, including: a.) Impedance Matching.
When coupling amplifier stages together impedance matching is important so that as much signal as possible is transferred from the output of one stage to the input of the next, keeping inter stage losses to a minimum.
b.) Correct Frequency Response.
Ensuring that the correct bandwidth is maintained throughout all stages of amplification. c.) DC Isolation.
It may be required that where the
An amplifier with two or more stages arranged in a manner that the output of one serves as the input for the next, while amplifying at each step. It is also called cascade amplifier.
EXPLANATION:
In most of the cases the gain provided by a single stage amplifier stage is insufficient. Consequently two or more amplifier stages are cascaded in order to increase the gain. Several amplifiers can be connected in a cascaded arrangement with the output of one amplifier driving the input of the next. Each amplifier in cascaded arrangement is known as stage. The basic purpose of multistage arrangement is to increase the voltage gain. It is understood that combining amplifiers of various types we can create those characteristics that are necessary to fulfill the specifications of a specific application.
GAIN FOR MULTISTAGE:
The overall gain of a multistage amplifier is the product of the gains of the individual stages (ignoring potential loading effects):
Gain (A) = A1* A2*A3 *A4 *... *An.
Alternately, if the gain of each amplifier stage is expressed in decibels (dB), the total gain is the sum of the gains of the individual stages:
Gain in dB (A) = A1 + A2 + A3 + A4 + ... An BANDWIDTH: The cascading in amplifiers obviously increases the gain. At the same time it also affects the bandwidth of an amplifier. And bandwidth decreases as the number of stages increase.
The way in which the individual stages are coupled together is important. The design of the coupling circuitry must fulfill several requirements, including: a.) Impedance Matching.
When coupling amplifier stages together impedance matching is important so that as much signal as possible is transferred from the output of one stage to the input of the next, keeping inter stage losses to a minimum.
b.) Correct Frequency Response.
Ensuring that the correct bandwidth is maintained throughout all stages of amplification. c.) DC Isolation.
It may be required that where the