1、CH3 LOGIC GATESLogical operation2. Application3. Troubleshooting of logic gates4. WaveformsChapter overviewThe standard logic symbol3-1 The InverterDistinctive shape symbolsRectangular outline symbolsThe negation indicatorsThe polarity indicators2. Truth table Inputs outputs A X 0 1 1 03. Operation4

2、. Timing diagram5. Logic expression:6. Application example: 1s complement circuit1. The standard logic symbolABX3-2 The And GateDistinctive shape XABRectangular outline 3. AND OperationIf inputs A and B are HIGH, output X is HIGH; If either A or B is LOW, or if both A and B are LOW, X is LOW 4. Trut

3、h table Inputs outputs A B X 0 0 0 0 1 0 1 0 0 1 1 1Table 3-2 Truth table for a 2-input AND gate3. Pulsed Operation Omission(P105,e.g. 3-3)ABX X=AB Or 4. Logic expressionBoolean multiplication5. Application exampleThe AND Gate as an Enable/Inhibit Device Fig. 3-15 p1081. The standard logic symbol3-3

4、 The OR Gate1XABRectangular outline XABDistinctive shape symbol2. Logical Operationif either input A or B is HIGH, output X is HIGH if both A and B are HIGH; X is HIGH if both A and B are LOW, X is low .3. Truth table Inputs outputs A B X 0 0 0 0 1 1 1 0 1 1 1 14. Pulsed OperationABX5. Logic express

5、ion X=A+BBoolean addition is the same as the OR function4. Application exampleFig. 3-24Intrusion detection and alarm systemThe NAND is a universal gate ,It can be used in combination to perform the AND, OR, and inverter operations.3-4 The NAND GateThe standard logic symbolRectangular outline symbolX

6、ABXABDistinctive shape symbol The standard logic symbolLogical OperationTruth tablePulsed OperationLogic expression (Omisssion)3-5 The NOR Gate3-6 The EXCLUSIVE-OR and EXCLUSIVE-NOR Gates=1XABXABThe standard logic symbolCMOS: Complementary Metal-Oxide Semiconductor Widely used in VLSI, ULSI 3-7 Inte

7、grated circuit logic gatesCMOS and TTL are the most widely used IC technologies, ECL is used in more specialized applications 400074HC 74HCT74VHC 74VHCT速度慢與TTL不兼容抗干擾功耗低74LVC 74AUC速度加快與TTL兼容負載能力強抗干擾功耗低速度兩倍于74HC與TTL兼容負載能力強抗干擾功耗低低(超低)電壓速度更加快與TTL兼容負載能力強抗干擾功耗低2. TTL: Transistor-Transistor LogicUsed in MSI, LSI74LS series 74 series74AS series 74ALS series3-7 Performance characteristics and parameters輸出高電平+VDD VOH(min)VOL(max) 0 G1門vO范圍 vO 輸出低電平