1 ECE2030 Introduction to Computer Engineering Lecture 4: CMOS Network Prof. Hsien-Hsin Sean Lee School of ECE Georgia Institute of Technology
H.-H. S. Lee 2 CMOS Inverter Connect the following terminals of a PMOS and an NMOS Gates Drains V in V out V dd Gnd V out V in V in = HIGH V out = LOW (Gnd) ON OFF V dd Gnd V out V in V in = LOW V out = HIGH (V dd ) ON OFF V dd PMOS Ground NMOS
H.-H. S. Lee 3 CMOS Voltage Transfer Characteristics V dd Gnd V in V out PMOS NMOS OFF: V_GateToSource < V_Threshold LINEAR (or OHMIC): 0< V_DrainToSource < V_GateToSource - V_Threshold SATURATION: 0 < V_GateToSource - V_Threshold < V_DrainToSource Note that in the CMOS Inverter V_GateToSource = V_in
H.-H. S. Lee 4 Pull-Up and Pull-Down Network CMOS network consists of a Pull- UP Network (PUN) and a Pull- Down Network (PDN) PUN consists of a set of PMOS transistors PDN consists of a set of NMOS transistors PUN and PDN implementations are complimentary to each other PMOS NOMS Series topology Parallel topology …. I0I0 I1I1 I n-1 OUPTUT V dd PUN Gnd PDN
H.-H. S. Lee 5 PUN/PDN of a CMOS Inverter AB 01 1Z AB 0Z 10 AB Pull-Up Network Pull-Down Network Combined CMOS Network V dd A Gnd B CMOS Inverter
H.-H. S. Lee 6 Gate Symbol of a CMOS Inverter V dd A Gnd B CMOS Inverter AB B = Ā
H.-H. S. Lee 7 PUN/PDN of a NAND Gate ABC Z ABC 00Z 01Z 10Z 110 Pull-Up Network Pull-Down Network V dd A B A B C
H.-H. S. Lee 8 PUN/PDN of a NAND Gate ABC Z ABC 00Z 01Z 10Z 110 ABC Pull-Up Network Pull-Down Network Combined CMOS Network V dd A B A B C
H.-H. S. Lee 9 NAND Gate Symbol ABC V dd A B A B C A B C Truth Table
H.-H. S. Lee 10 PUN/PDN of a NOR Gate ABC Z 10Z 11Z ABC 00Z Pull-Up Network Pull-Down Network V dd A C B A B
H.-H. S. Lee 11 PUN/PDN of a NOR Gate ABC Z 10Z 11Z ABC 00Z ABC Pull-Up Network Pull-Down Network Combined CMOS Network A C B A B V dd
H.-H. S. Lee 12 NOR Gate Symbol ABC A B C Truth Table A C B A B V dd
H.-H. S. Lee 13 How about an AND gate V dd A B A Gnd C NAND Inverter B C = A B A B C
H.-H. S. Lee 14 An OR Gate A B A B V dd Gnd C Inverter NOR A B C
H.-H. S. Lee 15 What’s the Function of the following CMOS Network? V dd C ABC 00Z Z ABC Z 10Z 110 ABC Pull-Up Network Pull-Down Network Combined CMOS Network XOR Function = XOR
H.-H. S. Lee 16 Yet Another XOR CMOS Network V dd C ABC 00Z Z ABC Z 10Z 110 ABC Pull-Up Network Pull-Down Network Combined CMOS Network XOR Function = XOR
H.-H. S. Lee 17 Exclusive-OR (XOR) Gate V dd C ABC A B C Truth Table
H.-H. S. Lee 18 XNOR How about XNOR Gate ABC A B C Truth Table How do we draw the corresponding CMOS network given a Boolean equation?
H.-H. S. Lee 19 XNOR How about XNOR Gate ABC A B C Truth Table V dd C XOR Inverter
H.-H. S. Lee 20 A Systematic Approach Each variable in the given Boolean eqn corresponds to a PMOS transistor in PUN and an NMOS transistor in PDN PUN Draw PUN using PMOS based on the Boolean eqn ANDseries AND operation drawn in series ORparallel OR operation drawn in parallel variable Invert each variable of the Boolean eqn as the gate input for each PMOS in the PUN PDN Draw PDN using NMOS in complementary form Parallel (PUN) to series (PDN) Series (PUN) to parallel (PDN) Label with the same inputs of PUN Label the output
H.-H. S. Lee 21 Example 1 In series In parallel Vdd (1) Draw the Pull-Up Network
H.-H. S. Lee 22 Example 1 In series In parallel Vdd (2) Assign the complemented input A C B
H.-H. S. Lee 23 Example 1 In series In parallel Vdd (3) Draw the Pull-Down Network in the complementary form A C B A C
H.-H. S. Lee 24 Example 1 In series In parallel Vdd (3) Draw the Pull-Down Network in the complementary form A C B A CB
H.-H. S. Lee 25 Example 1 In series In parallel Vdd Label the output F A C B A CB F
H.-H. S. Lee 26 Example 1 In series In parallel Vdd A C B A CB F ABCF Truth Table
H.-H. S. Lee 27 An Alternative for XNOR Gate ABC A B C Truth Table V dd C
H.-H. S. Lee 28 Example 3 Start from the innermost term A B D AC A D
H.-H. S. Lee 29 Example 3 Start from the innermost term A B D AC A D A C
H.-H. S. Lee 30 Example 3 Start from the innermost term A B D AC A D A C B
H.-H. S. Lee 31 Example 3 Start from the innermost term A B D AC A D A C B Vdd F Pull-Up Network Pull-Down Network
H.-H. S. Lee 32 Example 4 Start from the innermost term A B D A C A D A C B Vdd F E D E D Pull-Down Network Pull-Up Network
H.-H. S. Lee 33 Another Example How ??