How we interface TTL with CMOS?
One TTL IC can drive any number of CMOS ICs. However, TTL output in ‘high state’ yields 2.4 Volt which is lower than the minimum voltage required by CMOS IC (which is 3.5V) . For TTL to CMOS interfacing, standard pull up resistor is connected which solves the interfacing problem as mentioned.
Which logic family is faster TTL or CMOS?
TTL chips are generally faster than CMOS gates (but see ACT series), however there are two logic technologies faster than TTL-Emitter-coupled logic (ECL) and gallium arsenide (GaAs). These chips come at considerable cost in power consumption and ease of interface to other logic families.
What’s the difference between CMOS and TTL logic?
The TTL logic family uses bipolar transistors to perform logic functions and CMOS uses field effect transistors. CMOS generally consumes much less power, despite being more sensitive than TTL. CMOS and TTL are not really interchangeable, and with the availability of low power CMOS chips, TTL use in modern designs is rare.
Which is the second widely used digital integrated device after TTL?
CMOS logic gate circuit is the second widely used digital integrated device developed after the advent of the TTL circuit. With the improvement of the manufacturing process, the performance of the CMOS circuit may surpass TTL and CMOS may become the dominant logic device.
What makes up a TTL logic gate circuit?
TTL is mainly composed of a BJT (bipolar junction transistor a>) and a resistor. It has a fast speed. The earliest TTL gate circuit was the 74 series, and then the 74H series, 74L series, 74LS, 74AS, 74ALS and other series appeared. However, because TTL has large power consumption, it is gradually replaced by CMOS circuits.
What are the requirements for a TTL interface?
Similarly, in the HIGH state, the HIGH output current drive capability of the CMOS IC must equal or exceed the HIGH-level input current requirement of TTL IC. For a proper interface, both the above conditions must be met.