STABILIZED FEEDBACK AMPLIFIERS 



17 



260 



260 



24-0 



220 



200 



180 



160 



I 140 



20 100 1000 10000 20000 



FREQUENCY IN CYCLES PER SECOND 



Fig. 11 — Phase shift, delay, and delay distortion with and without feedback for a 

 single tube voice frequency amplifier. 



were made on an experimental one-tube amplifier, 35-8500 cycles, 

 feeding back around the low side windings of the input and output 

 transformers. 



Figure 12 gives the gain-frequency characteristic of an amplifier 

 with and without feedback when in the jS-circuit there was an equalizer 



100 



80 



5000 10,000 



FREQUENCY IN CYCLES PER SECOND 



50.000 100.000 



Fig. 12 — (iain-frequency characteristic of an amplifier with an equalizer in the 

 /3-circuit. This was designed to have a gain frequency characteristic with feedback 

 of the same shape as the loss frequency characteristic of a non-loaded telei)hone cable. 



