You are given two amplifiers, A and B, to connect in cascade between a 10-mV, 10

Question

You are given two amplifiers, A and B, to connect in cascade between a 10-mV, 100-k source and a 100- load. The amplifiers have voltage gain, input resistance, and output resistance as follows: for A, 100 V/V, 100 k, 10 k, respectively; for B, 10 V/V, 10 k, 1 k, respectively. Your problem is to decide how the amplifiers should be connected. To proceed, evaluate the two possible connections between source S and load L, namely, SABL and SBAL. Find the voltage gain for each both as a ratio and in decibels. Which amplifier arrangement is best?

Explanation / Answer

The amplifiers have voltage gain, input resistance, and output resistance as follows:
For amplifier A: 100V/V, 10 KOHMand 10KOHM respectively.
For amplifier B: 1V/V, 100 kohm and100KOHM respectively

Arrangement 1: SABL

As they are cascaded, Net voltage gain will same in both the cases that will be product of gain of the two= 1000

Input impedance in SABL will be of 10 kohm due to opamp A.

output impedance will be of B i.e. 100kohm.

Arrangement 2: SBAL

Voltage gain no doubt the product of the two as they are connected in cascaded=1000

Here Input impedance: 100kohm as b is towards input side

and output impedance : 10kohm as A is at output side.

BEST ARRANGEMENT : arangement SBAL

ALL OPAMPS SUFFERS FROM impedance mismatching is known as loading effect.

Thus to avoid loading effect the input resistance of amplifier should be as high as possible while the output resistance of the amplifier should be as low as possible.

hence SBAL is the best arrangement.

Related Questions

Navigate

• Browse (All)
• Browse Y
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.