COMPUTING

Chapter 7 Pulse Circuits and Waveform GeneratorsExample 7.3For the astable multivibrator circuit of Figure 7.16 compute the timing periods given thatC = 0.1 μF , R f = 50 KΩ , R 1 = 10 KΩ , R 2 = 50 KΩ , V ( + ) sat= 10 V , and V( −) sat= – 5 V.Cv( −)R fV + ( ) satv ( + )R 2v outv outtV( −) satR 1Solution:From (7.18) the attenuation factor is( a) ( b)Figure 7.16. Unstable multivibrator circuit for Example 7.3and with (7.20) and (7.21)aR 110= ---------------------- = -------------------- =( R 1 + R 2 ) 10 + 5001--6t 1 R f C V ( + ) sat– aV( −) = ln---------------------------------------sat= 50 × 10 4× 0.1 × 10 – 6 10 – ( 1 ⁄ 6)(–5)V ( + ) sat( 1 – a)ln -------------------------------------⎝⎛ 10 × ( 1 – 1 ⁄ 6)⎠⎞= 5× 10 – 2ln 65 ------------⁄ 6⎝⎛ 50 ⁄ 6 ⎠⎞ = 1.31 mst 2 R f C V( −)sat– aV ( + )= ln---------------------------------------sat= 50 × 10 4× 0.1 × 10 – 6 – 5 – ( 1 ⁄ 6)( 10)V( −) sat( 1–a)ln --------------------------------------⎝⎛ – 5 × ( 1–1 ⁄ 6)⎠⎞= 5 × 10 – 2ln – ---------------40 ⁄ 6⎝⎛ – 25 ⁄ 6 ⎠⎞ = 2.35 ms7.4 Monostable (One−Shot) MultivibratorsA monostable or one−shot multivibrator is an electronic circuit with two output states in which onlyone state is stable. This circuit stays in its normal state (usually a logical 0) until a signal isapplied to its input. When triggered by an input signal, the output reverses states, that is, changesfrom 0 to 1 for a short period of time, depending upon the circuit parameters which are discussedbelow, and then returns to its normal state.7−14Electronic Devices and Amplifier Circuits with MATLAB Computing, Second EditionCopyright © Orchard Publications