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To increase gain usually large collector resistance VALUE as gain is proportional to load resistor. However, DUE to limitation of maximum value load resistor, active loads are USED in amplifier to obtain large gain in INTERMEDIATE stages of amplifier.

To increase gain usually large collector resistance value as gain is proportional to load resistor. However, due to limitation of maximum value load resistor, active loads are used in amplifier to obtain large gain in intermediate stages of amplifier.

Level shifter is basically a SIMPLE TYPE emitter follower. Hence, level shifter ALSO act as a buffer to ISOLATE high gain stages from the output stage. Therefore, the amount of SHIFT obtained is

VO – Vi = -VBE = -0.7v.

Level shifter is basically a simple type emitter follower. Hence, level shifter also act as a buffer to isolate high gain stages from the output stage. Therefore, the amount of shift obtained is

VO – Vi = -VBE = -0.7v.

Due to cascaded stage, Darlington differential AMPLIFIER OFFERS HIGHER offset voltage which is two TIMES larger than ordinary two transistor USED in differential amplifier.

Due to cascaded stage, Darlington differential amplifier offers higher offset voltage which is two times larger than ordinary two transistor used in differential amplifier.

HIGHER value of input resistance can be obtained by using DARLINGTON PAIR in place of TRANSISTOR.

Higher value of input resistance can be obtained by using Darlington pair in place of transistor.

Overall CURRENT GAIN, β= β1×β2 (MULTIPLICATION of current gain of individual TRANSISTOR)

⇒ β=200×200=40000

Overall current gain, β= β1×β2 (Multiplication of current gain of individual transistor)

⇒ β=200×200=40000

The OUTPUT RESISTANCE of WILSON current mirror is substantially GREATER than ≅(β× Output resistance)/2 than SIMPLE or Widlar current source.

The output resistance of Wilson current mirror is substantially greater than ≅(β× Output resistance)/2 than Simple or Widlar current source.

In the widlar CURRENT SOURCE Re is ADDED to EMITTER lead of transistor, which consequently results in smaller output current VALUE.

In the widlar current source Re is added to emitter lead of transistor, which consequently results in smaller output current value.

The equation for TOTAL CURRENT is obtained by APPLYING Kirchhoff’s Voltage LAW to constant current circuit in differential AMPLIFIER.

The equation for total current is obtained by applying Kirchhoff’s Voltage Law to constant current circuit in differential amplifier.

For a large CMRR value, ACM should be SMALL as possible.

For a large CMRR value, ACM should be small as possible.

The BASE emitter VOLTAGE of transistor (VBE) in constant current CIRCUIT by 2.5mv/oc, thus diode ALSO has same TEMPERATURE. Hence two variations cancel each other and total current IQ become in depend of temperature.

The base emitter voltage of transistor (VBE) in constant current circuit by 2.5mv/oc, thus diode also has same temperature. Hence two variations cancel each other and total current IQ become in depend of temperature.

Constant CURRENT bias offers extremely LARGE resistor under AC condition and THUS provide high CMRR VALUE.

Constant current bias offers extremely large resistor under AC condition and thus provide high CMRR value.

Formula for differential mode gain USING ‘h’ PARAMETER MODEL for a single ended output.

Formula for differential mode gain using ‘h’ parameter model for a single ended output.

In PRACTICAL SITUATION, ARBITRARY signal are signal are represented as Sum and Difference of COMMON mode signal and differential mode signal.

In practical situation, arbitrary signal are signal are represented as Sum and Difference of common mode signal and differential mode signal.

In differential amplifier due to symmetry, both TRANSISTORS are BIASED and MATCHED. THEREFORE, Voltage at each collector will be same.

In differential amplifier due to symmetry, both transistors are biased and matched. Therefore, Voltage at each collector will be same.

Due to SYMMETRY of differential AMPLIFIER circuit, current IQ DIVIDES equally through both transistors.

Due to symmetry of differential amplifier circuit, current IQ divides equally through both transistors.

Any undesired noise, common to both of the input TERMINAL is suppressed by DIFFERENTIAL AMPLIFIER.

Any undesired noise, common to both of the input terminal is suppressed by differential amplifier.

For example, consider a single voltage SUPPLY +15v. During POSITIVE HALF cycle the output will be +5v and -10V during negative half cycle.

For example, consider a single voltage supply +15v. During positive half cycle the output will be +5v and -10v during negative half cycle.

The GAIN STAGES in Op-amp are DIRECT coupled. So, LEVEL SHIFTER is used for adjustment of DC level.

The gain stages in Op-amp are direct coupled. So, level shifter is used for adjustment of DC level.

Clamper is an external circuit connected at the OUTPUT of OPERATIONAL AMPLIFIER, which clamp the output to desire DC level.

Clamper is an external circuit connected at the output of Operational amplifier, which clamp the output to desire DC level.

Direct CONNECTION between stages removes the lower cut off frequency IMPOSED by coupling capacitor; therefore it can amplify both AC and DC SIGNAL.

Direct connection between stages removes the lower cut off frequency imposed by coupling capacitor; therefore it can amplify both AC and DC signal.

When two input signals are APPLIED to base of transistor, it is SAID to be DUAL Input. When both collectors are at same DC potential with respect to GROUND, then it is said to be BALANCE Output.

When two input signals are applied to base of transistor, it is said to be Dual Input. When both collectors are at same DC potential with respect to ground, then it is said to be Balance Output.