| 摘要 |
1,184,513. Transistor gating circuits. NIPPON GAKKI SEIZO K.K. 17 April, 1968 [19 June, 1967], No. 18232/68. Heading H3T. [Also in Division G5] A transistor gating circuit for use in an electronic musical instrument in which an envelope forming circuit (6) (Fig. 3, not shown) is used to control a transistor amplifier arranged in such a way that the tone generator can be connected to the input of the circuit without the need for voltage dividing circuits. The circuit also provides high input and output impedances which facilitate the connection of other units to the circuit. As shown a front stage T30 is connected either directly (Fig. 3, not shown) or via a semi-conductor device to a rear stage including a conventional envelope forming circuit including a key switch and connected through resistors Re3 and Re4 to the front and rear stages respectively. Fig. 4 shows the relationship of the circuit to a plurality of other circuits of identical type, as indicated in abbreviated form. By inserting the transistor T41 between the front and rear stages the baseemitter capacitances of each of the four transistors are in series and this results in a lower leakage current at the output terminal 4 when the circuit is cut-off. Figs. 5a to 5i (not shown) illustrate alternative embodiments in which the transistors T31 and T41 are replaced by one or two diodes or transistors in various combinations, while Fig. 5j (not shown) illustrates a circuit similar to Fig. 4 in which transistor T41 is also fed by the envelope-forming circuit through resistor (Re41). |
