TTL to CMOS and CMOS to TTL Conversion

This page explains how to convert between TTL and CMOS logic levels. We’ll cover both TTL to CMOS converters and CMOS to TTL converters.

TTL to CMOS Converter

Figure 1: Simple TTL to CMOS converter

As shown in Figure 1, a TTL to CMOS converter does exactly what its name suggests: it converts TTL signal levels to CMOS signal levels. In essence, it’s a level converter. TTL logic typically uses voltage levels around 3V, while CMOS logic often operates around 5V.

CMOS to TTL Converter

Figure 2: CMOS to TTL converter IC

The CMOS to TTL converter performs the opposite function. It converts CMOS signal levels to TTL signal levels. You can often use the same cables for both types of conversion, provided you have the appropriate mating connectors.

Logic Level Comparison

Here’s a table summarizing the key differences in logic levels between TTL and CMOS:

TTL to CMOS and CMOS to TTL converters are particularly useful when interfacing a 3V system with a 5V system, or vice versa. It’s important to note that the terms “TTL” and “CMOS” are often used to refer to 3V and 5V systems, respectively, because their logic levels are typically close to these supply voltages.

These converters typically incorporate buffers at the input and output pins, with a level converter stage in between. They’re also often referred to as voltage level shifters due to their primary function.

For more in-depth information, you can explore TTL and CMOS interfacing concepts.

Figure 2 above shows an example of a CMOS to TTL converter IC. This particular IC houses 6 inputs (A_IN, B_IN, C_IN, D_IN, E_IN, F_IN) and 6 outputs (A_OUT, B_OUT, C_OUT, D_OUT, E_OUT, F_OUT), along with Vcc, Vdd, and ground pins.