GB646647A - Improvements in and relating to thermionic valve amplifiers - Google Patents

Abstract

646,647. Pulse amplifying systems. MINISTER OF SUPPLY. April 14, 1947, No. 9878. [Class 40 (vi)] In a pulse amplifying circuit a voltage is produced which is proportional to the amplitude of an input pulse and which remains substantially constant between pulses, this voltage is then amplified and output pulses are produced whose amplitude is proportional to the amplified voltage. The Figure shows a pulse amplifier in which input pulses are applied to a pre-amplifier 1 together with pulses of reversed polarity obtained via the negative feed-back path 5, 6. The output of the preamplifier has a wave-form which between the transient portions has an amplitude proportional to that of the input pulses. A pulse generator 7 which may be synchronized by the input pulses produces a chopping pulse 9 which is in phase and of the same duration as the input pulse and a " strobe " pulse which has a leading edge which is delayed with respect to the leading edge of the input pulse and which is of much shorter duration than the input pulse. Both the pulses 8 and 9 are of fixed and predetermined amplitudes which are independent of the amplitude of the input pulses. The strobe pulses 8 are applied to a gate and peak rectifier circuit 2 which comprises a diode clamp circuit which is opened by the strobe pulses 8 so that the voltage from the pre-amplifier charges a capacitor in the clamp circuit to a level which is proportional at any input to the amplitude of the applied pulse, i.e. to the amplitude of the input pulse present at that instant. The D.C. signal present at the output of unit 2 is amplified in the D.C. amplifier 3 and applied to unit 4 which is similar to the diode clamp circuit of unit 2. The clamp is opened by the chopping signal 9 from generator 7 so that an output pulse is produced which is an amplified replica of the input pulse, this pulse has its polarity reversed in unit 5 and is applied back to the input via unit 6. The amplifier may be used in an analogue computing system ; the several variables which are to be computed being expressed as amplitude modulated pulses on a time-division multiplex system which are amplified in a circuit as described and applied to a magslip resolver the negative feed-back voltage being supplied from a suitable pick-up winding on the magslip. In a modification the strobe and chopping pulses occur at a sub-multiple of the input pulse repetition frequency so that the output amplified pulses have a lower repetition frequency than those at the input.