Логикалық емес қақпасы және оның қолданылуы

Logic gate implementing negation

In digital logic, an inverter or NOT gate is a logic gate which implements logical negation. It outputs a bit opposite of the bit that is put into it. The bits are typically implemented as two differing voltage levels.

The inverter is a basic building block in digital electronics. Multiplexers, decoders, state machines, and other sophisticated digital devices may use inverters. The hex inverter is an integrated circuit that contains six (hexa ) inverters. For example, the 7404 TTL chip which has 14 pins and the 4049 CMOS chip which has 16 pins, 2 of which are used for power/referencing, and 12 of which are used by the inputs and outputs of the six inverters (the 4049 has 2 pins with no connection).

Digital inverter quality is often measured using the voltage transfer curve (VTC), which is a plot of output vs. input voltage. From such a graph, device parameters including noise tolerance, gain, and operating logic levels can be obtained. Ideally, the VTC appears as an inverted step function – this would indicate precise switching between on and off – but in real devices, a gradual transition region exists. The VTC indicates that for low input voltage, the circuit outputs high voltage; for high input, the output tapers off towards the low level. The slope of this transition region is a measure of quality – steep (close to vertical) slopes yield precise switching. The tolerance to noise can be measured by comparing the minimum input to the maximum output for each region of operation (on / off).

Since the transition region is steep and approximately linear, a properly biased CMOS inverter digital logic gate may be used as a high gain analog linear amplifier or even combined to form an opamp. Maximum gain is achieved when the input and output operating points are the same voltage, which can be biased by connecting a resistor between the output and input.