TTL and CMOS characteristics

Supply voltage. 

The bipolar TIT, fami-lies require +5 volts, +5%, whereas the CMOS families have a wider range: +2 to +6 volts for HC and AC, +3 to +15 volts for 4000B and 74C. The HCT and ACT CMOS families, designed for compatibility with bipolar TTL (see below), require +5 volts. Input A TTL input held in the LOW state sources current into whatever drives it (0.25mA typ for LS), so to pull it LOW you must sink current. Since the TTL output circuit (a saturated npn transition) is good at sinking current, this presents no problem when TTL logic is wired together, but you must keep it in mind when driving TTL with other circuitry. By contrast, CMOS has no input current.

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Specific Kinds of Relays

Subminiature Relays

Typical mechanical relays are designed for switching relatively large currents. They come with either dc or ac coils. Dc-actuated relays typically come with excitation-voltage ratings of 6, 12, and 24 V dc, with coil resistances (coil ohms) of about 40, 160, and 650 Ω, respectively. Acactuated relays typically come with excitation-voltage ratings of 110 and 240 V ac, with coil resistances of about 3400 and 13600 Ω, respectively. Switching speeds range from about 10 to 100 ms, and current ratings range from about 2 to 15 A.

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Transistor Comparison With Electron Tubes

 a. Efficiency and Voltage Requirements. 

transistor power efficiency is greater than that of the electron tube because the transistor does not require heater power. In addition, it does not require warm-up time, and it does not require a large de voltage to operate. Other advantages of the transistor are its useful life (b below), its noise level (c below), and its size and construction (d below).

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5 Main Transistor Functions

 

 a. Amplification. 

The transistor may be used as a current, voltage, or power amplifier. For instance, a stronger signal current, may be obtained from a transistor than is fed into it. A signal of 1 milliampere fed into the input circuit of the transistor may appear as 20 milliamperes at its output. Various circuit arrangements provide for various amounts of signal amplification.

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