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在通常使用的交流耦合RC触发器中,小的RC时间常数是功率消耗主要原因(见图a)。例如,100ns的RC器件,消耗功率10mw一是两片LSTTL门的两倍多。但若按图(b)简单地重新连接R_2和R_1,其电路功耗减半而性能更佳。图(b)中的电阻接法消除了电路中RC网络不工作时的损耗。例如,当IC_(1a)的2脚输入是逻辑“0”时,R_1和R_2功耗为零,这是因为电阻的两端电压都是5V。同时,IC_(1b)的输出逻辑“0”让电流通过R_3和R_1并在5脚输入端产生3V电压(逻辑“1”)。负跳变加在C_2上触发该触发器;而类似的信号加在C_1上将再次触发触发器。值得一提的是:在电路中,未工作的RC网络把门电压提升到V_(cc)(不在门输入线性区,会增加功耗)。
In the commonly used AC-coupled RC flip-flop, a small RC time constant is the main cause of power consumption (see Figure a). For example, a 100ns RC device consumes more than twice the power of 10mW, one of two LSTTL gates. However, if simply reconnecting R_2 and R_1 as shown in (b), the power consumption of the circuit is reduced by half and the performance is better. The resistor connection in Figure (b) eliminates the loss of the RC network in the circuit when it is not operating. For example, when pin 2 of IC_ (1a) is a logic “0”, R_1 and R_2 consume zero power because the voltage across the resistor is 5V. At the same time, the output logic “0” of IC_ (1b) passes current through R_3 and R_1 and generates a 3V voltage (logic “1”) at the 5-pin input. A negative transition triggers the flip-flop on C_2; a similar signal on C_1 triggers the flip-flop again. It is worth mentioning that: in the circuit, the RC network does not work the door voltage to V_ (cc) (not in the linear input gate, will increase the power consumption).