COMPUTING

The InverterTABLE 6.2 The truth table for the inverterInputLHOutputHLWith positive logic, the truth table for the inverter is written as shown in Table 6.3.TABLE 6.3 The truth table for the inverter when positive logic is assumedInput Output0 11 0With negative logic, the truth table for the inverter is written as shown in Table 6.4.TABLE 6.4 The truth table for the inverter when negative logic is assumedInput Output1 00 1Figure 6.6 shows the TTL SN7404 Hex Inverter IC where SN identifies the packaging and Heximplies that there are 6 inverters within the IC.VccA6Y6 A5Y5A4Y41A1Y121413Vcc6A1413121110982A3126Y2Y4115A3A5 10 5Y3YGND67984A4Y1 2 3 4 5 67A1 Y1 A2 Y2 A3 Y3Figure 6.6. The SN7404 Hex Inverter ICGNDOne important parameter is the input clamp voltage denoted as V IK and this refers to the maximumnegative voltage that may be applied at the input terminals without damaging the IC. A typicalvalue for this parameter is – 1.2 V . To insure that this value is not exceeded, diode D 1 is includedto clamp the input voltage to less than –1.2 V with respect to the ground. We recall from Chapter2 that a practical diode, when forward−biased, may be represented as an ideal diode in series witha 0.7 V source and a small resistance as shown in Figure 6.7.Electronic Devices and Amplifier Circuits with MATLAB Computing, Second EditionCopyright © Orchard Publications6−3