2.90 An op-amp differentiator, employing the circuit shown in Fig. 2.27(a), has R = 20 k and C = 0.1 μF. When a triangle wave of ±1-V peak amplitude at 1 kHz is applied to the input, what form of output results? What is its frequency? What is its peak amplitude? What is its average value? What value of R is needed to cause the output to have a 12-V peak amplitude?