| 摘要 |
1337005 Gain control; pulse modulation systems VEREINIGTE FLUGTECHNISCHE WERKE-FOKKER GmbH 13 Nov 1970 [15 Nov 1969] 54238/70 Headings H3T H4L and H4R An amplifier circuit includes a network having two series-connected resistors, the network determining at least one parameter of the amplifier circuit, and periodic switching means of variable duty factor connected to the common point of the two resistors and so arranged as to switch periodically into and out of the network one of the resistors. Amplifier 32, Fig. 3, is provided with feedback by means of resistor 33, in conjunction with two series-connected resistors 30, 31, the junction point between which is periodically earthed by means of a switch 34 which may comprise a field-effect transistor. Switch 34 is controlled by a circuit 35 which produces a train of pulses whose width depends upon the value of the control voltage U st . The pulse repetition frequency is made higher than the frequency of the signal U e so that the effective value of the series resistors 30, 31 is proportional to the control voltage U st . The arrangement may be used in a three-term controller (Fig. 5, not shown). Circuit for producing width-controlled pulses.- A sawtooth wave is fed from source 15 via resistor 23 to one input of a comparator 16, and a control voltage U K via resistor 22 to the second input, sudh that whenever the sawtooth wave exceeds the control voltage U K an output U T is obtained from the comparator. The output pulses U T are also applied to a stabilizer 24, the output of which is fed via resistor 21, together with the control voltage U st to the input of an integrator comprising amplifier 18 with feedback over capacitor 19; the output from amplifier 18 comprises the control voltage U k . |
