ISSN 10637397, Russian Microelectronics, 2011, Vol. 40, No. 2, pp. 141–145. © Pleiades Publishing, Ltd., 2011.
Body biasing techniques control the voltage of
body of MOSFET to control and reduce leakage
power. In body biasing techniques basically
modulated to change
as can be seen from (1) which
shows various parameters that affect the threshold
voltage of a MOS transistor.
is the zero body bias threshold voltage and
mainly depends on the manufacturing process,
body effect coefficient (typically equals to 0.4
it depends on the gate oxide capacitance, silicon per
mittivity, doping level and other parameters.
surface potential at threshold (typically
is the sourcetobody voltage. The term
represent the effect of DrainInduced Barrier
Lowering (DIBL) in which
is the DIBL coefficient
and it is in the range of 0.02–0.1.
Subthreshold logic dissipates less power since the
is kept less than the threshold voltage
to ensure operation in the subthreshold region and
the fact that the circuit uses the small subthreshold (or
leakage) current of MOS transistors. Since the sub
threshold current depends exponentially on the gate
voltage, we expect an exponential increase in delay
[1–3]. The subthreshold current of the N (P)MOS
transistor is given by (2).
is a scaling current, proportional to mobility,
oxide capacitance per unit area and aspect ratio W/L,
n is the slope factor,
is MOSFET threshold voltage,
is gate voltage w.r.t body or substrate,
voltage w.r.t body and
is drain voltage w.r.t body.
Expression (2) also shows that the variation of the
of the transistor affects the
drain current. With a proper sourcetosubstrate volt
age the same drive current in the NMOS and PMOS
transistors can be achieved. In this paper a bodybias
technique to match the subthreshold currents of both
the NMOS and PMOS transistors is explored and a
Schmitt trigger employing this bias technique is pro
posed. By simulation it is shown that the Schmitt trig
ger with this body biasing is suitable for high perfor
mance and low power applications.
Subthreshold Schmitt Trigger Using BodyBias Technique
for Ultra Low Power and High Performance Applications
, Maneesha Gupta
, and Nupur Pzakash
Indira Gandhi Institute of Technology, Deptt. of Electronics and Communication Engineering, Kashmere Gate, Delhi, India
Netaji Subhash Institute of Technology Deptt. of Electronics and Communication Engineering, Dwarka, Delhi, India
Received May 09, 2010
—Digital subthreshold logic provides extremely low power consumption since the power supplies
are kept below the threshold voltage and using the small subthreshold current of MOS transistors to operate.
In this paper, a bodybias technique to match the subthreshold currents of both the NMOS and PMOS tran
sistors is explored and a Schmitt trigger circuit employing this bias technique is proposed. Extensive circuit
simulations were conducted and the results were compared with standard body bias technique in terms of per
formance parameters. The simulation results were obtained with 0.18
technology parameters. The con
clusion is that Schmitt trigger with this body biasing is suitable for high performance and ultra low power
The article is published in the original.