Active-compensated Non-inverting Amplifier:

In the recent past, there has been considerable research attempt in devising techniques for actively compensating for these effects (for instance see the references cited at the end of the section). The basic idea in all these works has been to alter known op-amp building blocks (using additional op-amps) in such a way that the modified circuits have decreased magnitude and phase errors as compared to the original ones. An exemplary compensated non-inverting amplifier is illustrated in Figure for which an analysis similar to the above yields

v₀  / v₁= (k1 + 1) { 1 + s τ2/ (1+   s τ₁ + s₂τ₁ τ₂ )]

where

τ₁ =     K₁  + 1 /  ω_ti , i = 1, 2

Figure: Active-compensated Non-inverting Amplifier

From Eq. the magnitude and phase errors (for τ₁ = τ₂ = τ, ω τ < < 1) are found to be

                    γ≅ ω² τ² 

and

                    φ≅ - ω³ τ³

Figure. As a result, the compensated non-inverting amplifier of Figure would operate satisfactorily over frequency ranges much higher (typically up to various hundred kHz) than the uncompensated amplifier of Figure. From the circuit of Figure, a compensated inverting amplifier is achievable by grounding the non-inverting inverting input terminal of A₁ ungrounding the resistor R₁ and applying the input at the node therefore created. Also a compensated buffer is achievable from the circuit of Figure by shorting resistors k₁ R₁ and k₂ R₂ and deleting R₁ and R₂.

Even though we have discussed only one exemplary circuit, a great number of two op-amp and three op-amp based compensated VCVS structures have been evolved up till now. For further information the interested reader is referred to the references cited at the end of this section. Also, the details of similar active compensation techniques evolved for developing the high frequency performance of other useful active circuit building blocks such as integrators, weighted-summers, VCCS, etc. can be found in the references quoted at the end. Therefore, a simple way of developing the high frequency performance of op-amp based building blocks therein by their active compensated versions. The application of this concept in extending the operational frequency range of op-amp RC filters and sinusoidal oscillators is well established now. Details about the improvement of the high frequency performance of well known filters, and the classical Wien bridge oscillator can be found in cited references.