electrical frequency generators for alternative production of rectangle, triangle, saegezahn and similar waves

摘要

1,078,881. Triangular wave generator circuits. SERVOMEX CONTROLS Ltd., and R. MUDIE. Aug. 13, 1965 [Aug. 31, 1964], No. 35620/64. Heading H3T. [Also in Division G4] A triangular wave generator comprises an RC integrator 7, 8, 9 fed with a square wave from a bi-stable circuit 5 through an amplifier 6 the output of the integrator being fed back to the input of the amplifier (via path 31) and the output of the amplifier being regeneratively fed back (via 21) to the input of the bi-stable circuit. The feedback arrangements allow the triangular wave to be generated without flattened peaks. In operation, when the trigger circuit provides a positive output at 2 an amplified positive step is applied to the feedback integrator 7, 8, 9 the transition at the step being speeded by feedback through resistor 21. Amplifier 7 is phase reversing so that the integrator provides a negative-going slope at output terminal 4 and this is fed back to the input of amplifier 6 so that this input is the difference between the positive step from the bi-stable circuit and the negative-going wave. When this reaches zero amplifier 6 ceases to provide an output so that the regenerative feedback through 21 also ceases. With the feedback path through 23, 24 to the input opened (as shown) a triggering pulse must be applied to one to cause the circuit to generate the positivegoing flank of the output wave. If, however, the terminals 23, 24 are bridged, the end of the negative-going slope will be such as to trigger the bi-stable circuit to initiate the production of the positive output slope and the circuit is accordingly free running. If alternatively the rectifiers 25 or 26 bridge the feedback terminals 23, 24 the circuit is monostable with a positive or negative rest condition depending upon which rectifier is selected. Diodes 11, 13 clamp the output of the bi-stable circuit and 15, 17 the output from the amplifier. The frequency may be adjusted by means of potentiometer 22, resistor 8SP11/SP or capacitor 9, the latter preferably being switchable. Diodes 29 or 30 may bridge the part 811 of the integrator resistance to provide a difference between positive and negativegoing slopes. The Specification describes in detail circuits 4, 5, 6 and 7 (as follows). The bi-stable circuit 5 (Fig. 2, not shown) comprises cross-coupled PNP, NPN transistors (49, 55) the latter having a constant current load transistor (59) and a collector output potential clamping circuit (11, 13). The circuit may be triggered by input signals at terminal (1), by the feedback circuit (previously described) from terminal (4), from a synchronizing input circuit (34) or by selector switch (33). The switching of the bi-stable circuit is speeded by a feedback circuit including amplifier (6) connected between terminals (2) and (3). The amplifier 6 (Fig. 3, not shown) comprises a long-tailed pair (63), 67) feeding an output stage (81) through an emitter follower (72) the output stage having a constant current collector load transistor (85) and its output potentials clamped by rectifiers (15), (17). Diodes (65, 66) limit the input signal which is formed from the combination of the square wave input at (2) and the triangular wave at (4). The amplifier 7 of the integrator may take three forms. In Fig. 4a (not shown) it comprises an electrometer valve input stage (90) having a variable bias provided by a resistor in the filament circuit. The output is fed through a three-stage transistor amplifier to an output circuit having a transistor constant current emitter supply (112). Temperature stabilization is effected by a diode circuit connected to bias the emitter of the first transistor stage. A feedback capacitor (9) and an input resistor (8SP1/SP, 8SP11/SP) are provided so that the circuit integrates the square wave voltage applied at (3) to provide a triangular output at 4. The part (8SP11/SP) of the integrating resistor may be shunted by a diode (29 or 30) to alter the integrator time constant for one polarity of signal and thus the slope of one flank of the output wave. Lead 31 provides feedback to a previous amplifier stage. In Fig. 4b (not shown) the part of the circuit preceding transistor (104) is replaced by a junction transistor long-tailed pair (120, 121) whereas in Fig. 4c (not shown) the input circuit is replaced by a M.O.S. type F.E.T. long-tailed pair (133, 134).