Richardson's handbook of projection (1930)

Record Details:

Title:
Richardson's handbook of projection
Date:
1930
Publisher:
New York : Chalmers Publishing Company
Volume:
Richardson's handbook of projection
Leaf #:
000293
Language:
English
Subjects:
Motion Pictures, Motion Picture Technology
Collection:
Books
Format:
Books
Contributor:
Media History Digital Library
Sponsor:
Media History Digital Library
Coordinator:
Media History Digital Library
Description:
Date Added:
August 01, 2024
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MANAGERS AND PROJECTIONISTS 1217 end of the secondary winding of an input transformer, and the grid of the second tube to the other end of this winding. Then, obviously, if there is A. C. flowing in the transformer winding, a half wave which appears ^ as positive to one grid will appear as negative to the other, and vice versa. You might say that one grid is pushing while the other is pulling, and they do this alternately. Hence this is called push-pull amplification. With this arrangement, even if a half wave gets too little amplification in the tube where it makes the grid negative, it will at the same time be getting too much amplification in the other tube where it makes the grid positive. The plate currents from both tubes combine their action in the plate circuit, and the result is that the distortion caused by one counterbalances that caused by the other, making the total output just about right. That is the principle of push-pull amplification. Of course, even this principle has its limit; if the two tubes are worked too hard, a point will be reached at which the distortion introduced on the negative half wave no longer balances that on the positive half wave, and then the total current will be distorted. However, as a general rule it may be said that two tubes working in push-pull will give about three times as much undistorted output as one tube, or 50 per cent more than they would give if simply connected in parallel. 10