Editing Transistor–transistor logic (section)

=== Analog applications ===
While originally designed to handle logic-level digital signals, a TTL inverter can be biased as an analog amplifier. Connecting a resistor between the output and the input biases the TTL element as a [[negative feedback amplifier]]. Such amplifiers may be useful to convert analog signals to the digital domain but would not ordinarily be used where analog amplification is the primary purpose.<ref>{{citation |last=Wobschall |first=D. |title=Circuit Design for Electronic Instrumentation: Analog and Digital Devices from Sensor to Display |edition=2d |location=New York |publisher=McGraw Hill |year=1987 |isbn=0-07-071232-8 |pages=209–211}}</ref> TTL inverters can also be used in [[crystal oscillator]]s where their analog amplification ability is significant.

A TTL gate may operate inadvertently as an analog amplifier if the input is connected to a slowly changing input signal that traverses the unspecified region from 0.8&nbsp;V to 2&nbsp;V. The output can be erratic when the input is in this range. A slowly changing input like this can also cause excess power dissipation in the output circuit. If such an analog input must be used, there are specialized TTL parts with [[Schmitt trigger]] inputs available that will reliably convert the analog input to a digital value, effectively operating as a one bit A to D converter.