Important/ Ideal characteristics or parameters of ideal OP-AMP

Infinite voltage gain $(AV= ∞)$ The open loop (without feedback) gain of an ideal OP-AMP is denoted by Av. It is the differential voltage gain and its value for ideal $OP-AMP →∞$

$V_0 =Av \times Vd$

As $Av=∞$, diff. voltage Vd required to obtained more o/p voltage $(±V_{cc})$ will be negligible i.e., $Vd = 0V.$

Infinite i/p resistance $(R_i=∞):$

The i/p rest is also called as differential i/p resistance and it is defined as total resistance measured between 2 i/p terminals of an op-amp.

The i/p resistance $R_i$ of an ideal OP – AMP is infinite. Due to this, the current flowing in each i/p terminal will be zero i.e., $I_{B1}=I_{B2}=0$.

Due to infinite i/p resistance, almost any source can drive it and the source does not get loaded.

Zero o/p resistance $(R_0=0)$:

The o/p resistance is viewed from o/p terminal as shown.

The o/p $R_0$ of ideal op-amp is 0. Due to 0, the ideal op-amp can drive infinite number of other devices.

Further, there will not be any change in its o/p voltage due to change in load current. That means its voltage regulations will be good.

Zero offset Voltage:

In practical, op- amp a small o/p voltage is present even though both the i/p $V_1$ and $V_2$ are having a zero value.

This voltage is called as offset voltage. For ideal OP-AMP the offset voltage is zero. That means o/p voltage will be zero when i/p is zero.

Bandwidth (infinite):

Bandwidth of an amplifier is the range of frequency. over which all sig frequency. are amplified almost equally.

The bandwidth of ideal op-amp is infinite. So it can amplify any frequency. sig from 0 to $∞ Hz$.

Thus the gain of an ideal amplifier is constant from 0 frequency (dc sig) to $∞ Hz$.

Infinite CMRR: For an OP-AMP, CMRR is defined as ratio of differential gain to common mode gain.

CMRR is ∞ for an ideal OP-AMP. Thus o/p voltage corresponding to common mode noise is zero.

Infinite Slew Rate (S= ∞) :

The slew rate of an ideal op-amp is infinite so that o/p voltage changes occur simultaneously with i/p voltage changes.

Zero Power supply rejection ratio (PSRR =0):

PSRR is a parameter which specifies the degree of dependence of OP-AMP o/p, on the changes in power supply voltage.

For an ideal OP-AMP, PSRR =0 , that means the o/p voltage does not change due to fluctuations in supply voltage.