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Single-Stage Degenerative Amplifier

Author: J.B. Hoag

Fig. 26 B. A simple degenerative amplifier

In Fig 26 B, the negative feedback voltage is transmitted through the condenser C1 and resistor R1 and appears across resistor R2. Suppose, for instance, that an input signal makes the grid of the tube less negative for a moment. The resultant increase of plate current produces a negative potential at the top of the primary of the output transformer. This is transmitted through R1C1 to R2. The top of R2 becomes negative for a moment, and, through the secondary of the input transformer, makes the grid negative, the reverse of the positive impulse of the input signal.

Fig. 26 C. Another simple degenerative amplifier

In Fig. 26 C, the cathode resistor R2 is used simultaneously to provide the C-bias and for the feedback purpose. When a positive impulse occurs on the grid, the plate current increases; and also the ir drop in R2 increases because it is in the plate circuit. An increase of voltage across R2 makes the grid more negative, the reverse of that of the signal voltage.

Last Update: 2009-11-01