P2.25 H. S. Black is noted for developing a negative feedback amplifier in 1927. Often overlooked is the fact that three years earlier he had invented a circuit design technique known as feedforward correction

[19]. Recent experiments have shown that this technique offers the potential for yielding excellent amplifier stabilization. Black’s amplifier is shown in Figure P2.25

(a) in the form recorded in 1924. The block diagram is shown in Figure P2.25(b). Determine the transfer function between the output Y1s2 and the input R1s2 and between the output and the disturbance Td(s). G1s2 is used to denote the amplifier represented by m in Figure P2.25(a).

FIGURE P2.25 H. S. Black's amplifier. (a) Ta(s) + R(s) G(s) + G(s) G(s) (b) Y(s)