CMOS Analog Integrated Circuits

8.11  Effects of the amplifier finite gain and bandwidth

Integrators are commonly used in filter design. In this analysis, the stray-insensitive circuit of Figure 8.47 is considered. It can operate as an inverting SC integrator when the switch timings are S₁(ϕ₂) and S₂(ϕ₁), or a noninverting SC integrator when switch timings are S₁(ϕ₁) and S₂(ϕ₂). The amplifier will have, as in practice, an open loop gain, A, with a finite dc gain ⁷, A₀, and a finite transition frequency (or unity-gain frequency), f_t. Thus, the inverting input terminal, υ⁻, of the amplifier will not be a true virtual ground but will be dependent on the output signal, as υ₀ = A(υ⁺ – υ⁻).

FIGURE 8.47Lossless discrete-time stray-insensitive integrator.

The equivalent models of ...