what is ideal op-amp? | characteristics of ideal op-amp

In this blog today we see what is ideal op amp and characteristics of the ideal operational amplifier.

what is operational amplifier?

operational amplifier is a versatile device that can perform different algebraic operations like addition, subtraction, multiplication, integration, differentiation etc.  

ideal operational amplifier

an ideal operational amplifier is a differential amplifier which have infinite open-loop gain, infinite input impedance, zero output impedance, infinite bandwidth, and a zero noise.

characteristics of ideal operational amplifier

1. infinite open loop gain

open loop gain is also define a gain without feedback because we do not connect any feedback between the output and input.

it is denoted by Av

formula for the voltage gain is    

the gain is infinite to get the maximum voltage that is +Vcc or -VCcc.

in the infinite open loop gain the gain is so high because of it is parently designed to have high gain using multistage differential amplifier

2. infinite input impedance

infinite input impedance is simply means that the impedance or resistance on the input terminals is open circuited due to this current flowing in input terminal is 0.

therefore it means that no current flow from the circuit. and i.e. Ib1 = Ib2 = 0

in infinite input impedance the op-amp can be driven by almost any source.

and because of open circuit there do not have any force or loading.

3. zero output impedance

the output impedance or resistance is zero R0 therefore there will not any change in output voltage due to the load current changes.

it is simply that output voltage is not change when load current is changed. 

that means it can drive any numbers  of load or device ideally.

4. infinite bandwidth

bandwidth is a range of frequency of the device which can amplified almost equally.

the bandwidth is infinite means the device can amplify all type of frequency signals which is zero to infinite.i.e. 0 Hz to ∞ Hz

therefore gain of amplifier is constant between zero to infinite.

because of infinite bandwidth it can amplify A.C. as well as D.C. signals.

5. zero offset voltage

offset voltage is the small output voltage present when the input voltage is zero.

this output voltage is zero in the case of ideal operational amplifier this zero voltage is called the zero offset voltage.

ideally offset voltage is zero means zero output voltage for zero input voltage i.e.V1 = V2 = 0 

6. infinite CMRR

CMRR is the ability of the operational amplifier to reject the common mode signals.

and the common mode gain is a noise signals that equally appears on the two terminals.

the ratio of differential gain to common mode gain is defined as CMRR.

infinite CMRR gain ensure zero common mode gain. 

therefore in the ideal operating amplifier common mode gain output is zero.

and the formula of CMRR is  = Ad/AC.

                                                =  differential gain / common mode gain.

7. infinite slew rate

infinite skew rate is the change occurs in the output simultaneously with the change in the input.

the skew rate of an ideal operational amplifier is infinite.

8. zero PSRR

PSRR is the power supply rejection ratio.

PSRR is the ratio or degree of the dependency of output voltage on change in the power supply.

the value of the PSRR is zero PSRR=0

it means that the according to PSRR it has no change in output according to the fluctuation in the power supply.

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