COMPUTING

Chapter 7 Pulse Circuits and Waveform GeneratorsLet us choose R A = 5.1 KΩ ; then R B = 5.1 ⁄ 2.363 = 2.16 KΩ . The value of the capacitor canbe found from either expression (7.11) or (7.14) but (7.11) is simpler. Thus, if we require that= 5 μs , then,T 1from whichT 1 = 5 × 10 – 6= 0.69R A C = 0.69 × 5.1 × 10 3CC5×10 – 6= ------------------------------------- = 1.42 n F0.69 × 5.1 × 10 3An unstable multivibrator can also be constructed with an op amp as shown in Figure 7.15.V +Cv( −)v ( + )R fR 2v out( ) satv +v outtV( −) sataV + ( ) sat( )( b)tR 1( a)aV − ( ) sataV + ( ) satv( −)( c)taV − ( ) satFigure 7.15. An unstable multivibrator using an op ampFrom the circuit of Figure 7.15(a), application of KCL at the non−inverting input of the op ampyieldsv ( + )–v------------------------ out v ( + )+ -------- = 0R 2R 1( d)( R 1 + R 2 )v( + )--------------------------------R 1 R 2=v--------- outR 2v ( + )---------v outR 1=( ---------------------- =R 1 + R 2 )a(7.18)7−12Electronic Devices and Amplifier Circuits with MATLAB Computing, Second EditionCopyright © Orchard Publications