Page 107 - Microsensors, MEMS and Smart Devices - Gardner Varadhan and Awadelkarim
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88 STANDARD MICROELECTRONIC TECHNOLOGIES
V CE =10V
30
20
10
Threshold
voltage
(a) 0 0.6 0.7 0.8
I c (mA)
,
Forward-active region
Breakdown
* N. region
Saturation
region
(On)
10 15
Cut-off region
Reverse-active region
(Off)
(b)
Figure 4.22 Input (a) and output (b) characteristic of a typical n-p-n transistor in the
common-emitter configuration
When (V BE — V CE) < — 0.1 V, the exponential term is small, and Equation (4.20)
reduces to
(4.21)
In the saturated region (V BE > 0, V BC > 0)> both junctions are forward-biased and the
transistor is switched ON (i.e. closed), with the output voltage V BE being close to zero.
Conversely, in the cutoff region (V BE < 0, V BC < 0), both junctions are reverse-biased
