What is the difference between the nand gate ic's 74ls00 and 74ls132?

Answer 1

The 74LS00 is a logic NAND gate with normal logic level inputs. This means that the inputs has a low range below 0.8V, unrecognised range and a high range above 2V. At any time a input signal crosses those levels, a change in state can be expected. Applicable to the LS family, they have a floating input that means it is uncertain the state of logic level if no input is connected. Therefore never assume that since the input is not connected that the circuit will assume a zero, it can be either zero or one.

The 74LS132 is also a NAND gate logic function. But different to the Logic level input it uses what we call a Schmitt trigger input to improve noise immunity in a circuit. In simple terms; it's really nothing more than a comparator input. But the Schmitt trigger also have a hysteresis, which help to eliminate the affect what noise have on the circuit.

On a more technical note

Each circuit contains a 2-input Schmitt trigger followed by a Darlington level

shifter and a phase splitter driving a TTL totem pole output. The totem pole is basically a push-pull output stage constructed with two p-n-p transistors and a diode on the output.

The comparator function would mean that there is a particular threshold level on the input and if the input voltage pass the particular level, the output or intermediate state of the function will change state. In the case of multiple logic inputs the change of input state does not necessarily mean a change in output state and therefore I will refer to an intermediate area inside the function related to the input state.

The hysteresis create a high and low trigger points. This cause the input to at least pass the high trigger point of about 1.6V before the intermediate state will change or drop below the 0.9V before the intermediate state change back again. Therefore the practical unit will not have one particular level to change state but these two fixed trigger points must be used.

It sounds like it complicates matters but it really helps to handle input noise signals which makes the Schmitt trigger a handy device. Making it a good device for signal conditioning of logic signals in some applications.

Also take note that the high and low hysteresis trigger points may vary with supply voltage. In fact I do not recommend it as standard practice to use a Schmitt trigger to evaluate analogue levels, some engineers may differ but I would rather refer to a real comparator circuit design where you have more control over precision, trigger points and reference levels. But may be considered for logic inputs from sensors or conditioning of logic signals

Some circuits may also employ Schmitt trigger devices for oscillators and contact debouncing

Answer 2

In the case of 7446, for Icex (HIGH Level Output Current (a thru g)), Vo = 30 V, while for 7447, Vo = 15V

Answer 3

LS is low power schottky. mostly these devices are lower power but about the same speed as standard devices.