Question 12.6: AUJT has characteristic as shown in Fig. 12.20(a) and the UJ......
AUJT has characteristic as shown in Fig. 12.20(a) and the UJT relaxation oscillator is shown in Fig.12.20(b) Find the values of : (a) Sweep amplitude, (b) the slope and displacement errors, (c) the duration of the sweep. and (Assume\ η = 0.6 and\ V_{F} = 0.7 V for silicon.)
The waveform of the sweep generator is shown in Fig. 12.20(c)
Given,\ V_{BB} = 15 V,\ V_{YY} = 30 V, R = 10 kΩ, C = 0.1 μF
We know that
\ V_{P} = η V_{BB} + V_{F} = 0.6 × 15 + 0.7 = 9.7 V.
From UJT characteristics, we have\ V_{V} = 1.6 V
(a) Amplitude of the sweep =\ V_{s} = V_{P} − V_{V}
= 9.7 − 1.6 = 8.1 V.
(b) Sweep speed error,
\ e_{s} = \frac{V_{s}}{V}= \frac{V_{s}}{V_{YY} − V_{V}}= \frac{8}{30 − 1.6} = 0.28 = 28%
Displacement error,\ e_{d} = \frac{1}{8}e_{s} = \frac{1}{8}(28) = 3.5%
(c) Sweep time,
\ T_{s} = RC \log_{e}\left( \frac{V_{YY} − V_{V}}{V_{YY} − V_{P}}\right) \ = 10 × 10^{3} × 0.1 × 10^{−6} × \log_{e}\left(\frac{30 − 1.6}{30 − 9.7}\right)
= 335.74 μs
