Differential input stage with separate feedback circuit and bias circuit

Using the circuit form shown in Figure 1-36, the feedback circuit and the bias circuit are separated, and Rfl is approximately 30fl. In order to ensure the amplification factor, R is set to lkflo , and a resistor R2 with the same resistance
as the base resistor R of the left tube is connected in series between the base of the right tube and Rtz , so that R2=Rl≈30kfIO, so that the bias current on both sides can be consistent, and The input resistance does not decrease either.