《电路》（英文版）3-4 Analog addition and subtraction

83-4 Analog addition and subtraction The addition circuit input -voltages R, 2 output-voltage R1 at node a 3 R 3 0。. 十 R R3 R (addition-circuit) U1+2 2 3 3 Let R1R3 and The result we have found for two R2/RIk, we have inputs may be extended to any U2=-k(U1+U3) number of inputs. R2,R2、,R2 if: k +U3+U4 RI R3

§3-4 Analog addition and subtraction The addition circuit 2 2 3 3 1 1 0, R R R a     −  =  + = 2 2 3 3 1 1 R R R at node a   a   a  a − = − + − : Let R1=R3 and R2 /R1= k, we have : 1 ( ) k = 2 = − 1 +3 if The result we have found for two inputs may be extended to any number of inputs. ( ) 4 4 2 3 3 2 1 1 2 2 = −  +  +  + R R R R R R output voltage input voltages − − − − − − 2 1 3 ,    ) R R R R ( 3 3 2 1 1 2  2 = −  +  ( ) 2 = −k 1 +3

As a example, if it is required to design a circuit to realize U,=-30,-20 R, KI 3 R 2 Ry 十 let:R=60k we=have 20k (addition-circuit) R R 30k 3 D,十 R I 3

and R k R k we have 30 20 3 1 = = − 3 2 3 2 1 2 = = R R and R R let : R2 = 60k ) R R R R ( 3 3 2 1 1 2  2 = −  +  2 = −31 − 23 As a example, if it is required to design a circuit to realize

The differential amplifier circuit The circuit may be analyzed by superposition. R By superposition R R R U21+D2y= y +(1+32) rI Ra+R, R2 +1 R RI R RI B IfR Ru,RhR2. 02=(U3-U If we require that D2=203-3U1 3+1 when, R2=RI 3→ 2 R R b b letr=30k we have R=R =R=lOk

The differential amplifier circuit By superposition: 3 1 2 1 1 2 2 21 2     (1 )  a b b y R R R R R R R + = + = − + + If Ra =R1 , Rb =R2 . ( ) 3 1 1 2 2 =  − R R 2 1 1 3 1 3 1 2 = = + + = → b a b a R R or R R R R 1 1 2 3 1 2 1 1   R R R R R R b a −             + + = let R2 = 30k we have R1 = Ra = Rb = 10k ( ) when,R R 2 3 1 2 1 → =  − = If we require that 2 = 23 − 31 The circuit may be analyzed by superposition