RESEARCH PAPER
International Journal of Recent Trends in Engineering, Vol 1, No. 3, May 2009
OTA-based Non-Inverting and Inverting
Precision Full-Wave Rectifier Circuits without
diodes
Nigar Minhaj
wave rectifier circuit is recently reported in technical literature
[7]. It uses a three-output CCCII, two MOS transistors and a
resistor with large cross over distortion for a low frequency of
5 KHz. Another rectifier circuit uses a fully differential input
and output operational transconductance amplifier (OTA),
four CMOS diodes and a MOS resistor in its realization,
which rectifies frequencies upto 200 MHz [8].
This work presents a precision full-wave non-inverting and an
inverting rectifier circuit using a three-output (two positive
outputs and one negative output) CMOS OTA, two
complementary MOS transistors and a resistor. The proposed
rectifier circuits have the following advantages:
1. No diodes are used in their realizations.
2. Rectifies high frequencies upto 200 MHz.
3. Input signal separating range is from −500mV to
500mV, and
4. Suitable for IC fabrication.
Abstract-- A three output operational transconductance
amplifier (OTA) with two complementary MOS transistors and a
grounded resistor is used to realize non-inverting and inverting
full-wave precision rectifiers. The attractive features of the
proposed rectifiers are; high input impedance, large input
operating range, high frequency operation, low zero crossing
distortion, linearity, low component count and suitable for IC
fabrication. SPICE simulation results, with 0.5 µm CMOS model
obtained through MIETEC, are included to verify the proposed
circuits.
Index Terms—Analog circuits; current conveyors; rectifiers.
R
I. INTRODUCTION
ECTIFICATION of low-level signals is a critical and
demanding aspect of analog signal processing in
telecommunication, instrumentation, measurement and
control. The main problem of the operation of diode-only
rectifier is limited by its threshold voltage. The precision
rectifiers based on operational amplifiers, diodes and resistors
exhibits significant distortion during the zero-crossing
transitional portion of the circuit’s operation due to smallsignal transient behaviour, restricting the upper frequency
limit of the circuit to a value well below that of the
operational amplifier employed.
The precision full-wave rectifiers consisting of current
conveyors, diodes and resistors have also been proposed due
to the advantages offered by these circuits [1-7]. Some of the
classical circuits use two current conveyors (CCII), diodes
and additional biasing network in form of voltage, source,
current source, or diode bias bridge. Some circuits employ
CCIIs, resistors, current conveyors, and current sources for
realization, whereas other recent works employ
CFA/operational conveyors, current conveyors and current
sources to realize a precision rectifier. A single currentcontrolled current conveyor (CCCII)-based precision full-
II. CIRCUIT DESCRIPTION
The proposed non-inverting precision full-wave rectifier
circuit is shown in Fig. 1. It consists of a single OTA with
three outputs (two positive outputs and one negative output)
as an active element, two complementary MOS transistors and
a resistor.
The OTA is used as a voltage to current converter (to change
the input voltage, Vin, into output currents Io1, Io2, Io3.
Complementary MOS transistors work as a voltage controlled
switch. The resistor RL is used as a current to voltage
converter, which converts the rectified currents into output dc
voltage, Vout. The relations of the positive and negative
polarity input voltage and output currents of the OTA can be
expressed as:
If Vin > 0 :
Io1 = + gm Vin
Io2 = + gm Vin
(1)
Vin < 0 :
Io3 = - gmVin
(2)
For switching the two CMOS transistors (Mn and Mp),
voltages ± Vsat are provided at their gates by connecting them
to a positive output terminal of the OTA.
Vsat corresponds to saturated voltage. Here, +Vsat equals to
VDD and –Vsat to Vss i.e., biasing voltage of the OTA.
Nigar Minhaj is with the University Women’s Polytechnic, Faculty of
Engineering and Technology, Aligarh Muslim University, Aligarh, India
(email: harun_ash@yahoo.com).
72
© 2009 ACADEMY PUBLISHER
RESEARCH PAPER
International Journal of Recent Trends in Engineering, Vol 1, No. 3, May 2009
The voltage ± Vsat produced at the gate of two MOS
IBIAS
transistors will be (±gmRp)Vin. Here Rp= Ro║RGP║RGN; Ro is
vin
I03 Mn
the output terminal resistance of the OTA, and RGP and RGN
+
-
IBIAS
vin
gm
I01 Mn
+
gm
+
-
-
v0ut
+
-
+
- vsat
Mp
Mp
RL
Proposed OTA-based inverting full-wave precision rectifier.
III. SIMULATION RESULTS
Proposed OTA-based non-inverting full-wave precision rectifier.
The proposed precision full wave rectifier circuit of Fig.1
and Fig. 2 are verified using the implementation of OTA [8]
as shown in Fig. 3. The parameters used in simulation are
0.5µm CMOS model obtained through MIETEC. The W/L
parameters of MOS-transistors are 25 µm / 1µm from M1 to
M10, 40µm /1µm for M11 to M20, 25 µm /2µm for MOS
transistor Mn, and 20 µm/2µm for MOS transistor MP and IBIAS
= 120µA. The supplied voltages used are VDD = - Vss = 5V,
VB = 2V and RL = 3K is taken. The effective resistance at the
gates of two MOS transistors is measured and found to be
400K. This is due to the parallel combination of the high
output impedance of the OTA along with the high impedance
gate terminals of MOS transistors. The simulated waveform of
the saturated gate voltage is shown in Fig. 4.
The input and rectified output for non-inverting full wave
rectifier of Fig. 1 is shown in Fig. 5 with input amplitude of
120mV and for frequencies of 1MHz, 50MHz and 200MHz.
The results of the inverting full wave rectifier of Fig. 2 are
shown in Fig. 6 at the same frequencies as for non-inverting
rectifier.
are the gate resistances of the Mp and Mn transistors
respectively. All these three resistances are quite high,
resulting in saturation at this output terminal of the OTA.
Depending upon the signal polarity (positive or negative) the
voltage at the gates is +Vsat or –Vsat, respectively.
The operation of the proposed circuit is as follows: In case of
positive half cycle input voltage, Vin > 0 and + Vsat = VDD. Mn
is ON (Mp is OFF). The output current Io1 (=gmVin) will flow
through the load, RL, resulting in positive polarity voltage at
Vout. In case of negative half cycle input voltage, Vin< 0 and
-Vsat = Vss, Mp is ON (Mn is OFF). The output current (Io3=
-gmVin) will flow through the load, , thus inverting the
negative cycle of input. Unidirectional current flows through
the load in either case, resulting in a full-wave rectified
output. Using (1) and (2), the relation between the input and
the output voltage of the proposed rectifier can be obtained as
Vin > 0 : Vo = + gmRLVin
(3a)
(3b)
Vin < 0 : Vo = - gm RLVin
Equation (3) shows that the transconductance gain of the OTA
can control the rectified output voltage. Thus, the circuit can
provide a control over the average (dc) output. Using eqn. 3
1
and gm =
, the relation between input and output voltages
RL
of the proposed non-inverting rectifier can be obtained as:
(4a)
Vin > 0 : Vout = + Vin
Vin < 0 : Vout = - Vin
(4b)
The inverting full-wave rectifier circuit can be realized from
Fig. 1 by simply reversing the connection of positive and
negative output terminals of the OTA, which are connected to
the complementary MOS transistors (i.e. Mn and Mp) as
shown in Fig. 2. The relation between input and output
voltages would become
Vin > 0 , Vout = -Vin
(5a)
Vin < 0 , Vout = Vin
(5b)
VDD
M19
M21
M20
M22
I02
M15
M13
VB
M16
I01
M14
M10
M18
M23
M24
I03
M2
IBIAS
M3
M5
M4
M6
M11
M7
M12
M8
VSS
(a)
73
M17
Vin
M1
M9
© 2009 ACADEMY PUBLISHER
RL
I03
Fig. 2.
Fig. 1.
+- v
sat
I01
+
I02
v0ut
I02
+
RESEARCH PAPER
International Journal of Recent Trends in Engineering, Vol 1, No. 3, May 2009
IBIAS
vin
I01
+
+
gm
I02
+
-
I03
-
(b)
Fig. 3. (a) MOS OTA structure with three-outputs, (b) Symbol of OTA with
three outputs.
The linearity of the proposed circuits is studied by applying
the dc input. The dc transfer characteristics is shown in Fig. 7,
which shows a high degree of linearity and equal swing for
both positive and negative variations of signal amplitude.
The operating voltage range is from – 500mV to 500mV, of
the input voltage. A little distortion at the zero crossing is
presented. It is mainly attributed to the ON/OFF switching of
the MOS transistors (Mn and Mp). The magnified zero
crossing of Fig. 1 is shown in Fig.8. A small distortion at zero
crossing is observed.
(b)
(c)
Fig. 5. Input (sinusoidal) and rectified output waveforms of non-inverting
full-wave precision rectifier of Fig. 1 at (a) 1MHz, (b) 50MHz and (c) 200MHz.
Fig. 4. Gate voltage waveform for Fig.1.
(a)
(a)
74
© 2009 ACADEMY PUBLISHER
RESEARCH PAPER
International Journal of Recent Trends in Engineering, Vol 1, No. 3, May 2009
(b)
Fig. 8.
Magnified zero-crossing of output (Vout) of Fig.1
IV. CONCLUSION
A non-inverting and inverting full-wave precision-rectifiers
are realized using a three-output operational transconductance
amplifier (OTA) with two complementary MOS transistors
and a grounded resistor. The attractive features of the
proposed full-wave rectifier circuit are high input
impedance, large input operating voltage range, high
frequency operation with low zero crossing distortion,
linearity, low component count and is suitable for IC
fabrication. SPICE simulation results, with 0.5 µm CMOS
model obtained through MIETEC verify the proposed circuit
operations satisfactorily.
(c)
Fig. 6. Input (sinusoidal) and rectified output waveforms of inverting fullwave precision rectifier of Fig. 1 at (a) 1MHz, (b) 50MHz and (c) 200MHz.
V. REFERENCES
[1]
[2]
[3]
[4]
[5]
[6]
Fig. 7. Simulated results for dc transfer characteristic for proposed precision
rectifier of Fig. 1.
[7]
[8]
Z. Wang. “Full-wave precision rectification that is performed in current
domain and very suitable for CMOS implementation.” IEEE
Transactions on Circuits and Suystems-I, 39, 456-462, 1992.
K. Hayatleh, S. Porta and F.J. Lidgey, “Temperature independent current
conveyor precision rectifier.” Electron. Lett. 30, 2091-2093, 1994
B. Wilson and V. Mannama, “Current mode rectifier with improved
precision.” Electron. Lett, 31, 247-248, 1995.
A. Monapapassorn, K. Dejhan and F. Cheevasuvit, “A fullwave rectifier
using a current conveyor and current mirrors.” Int. J. Electron. 88, 751758, 2001.
S.J.G. Gift. “An improved precision full wave rectifier.” Int. J. Electron.
89, 259-265, 2002.
S.J.G. Gift. “New precision rectifier circuits with high accuracy and
wide bandwidth.” Int. J. Electron. 92, 601-607, 2005.
S. Maheshwari, “Current controlled precision rectifier circuits”, Journal
of Circuits, Systems, and Computers, Vol. 16, no. 1, 129-138, 2007.
M. Kumngern and K. Dejhan, “High frequency and high precision
CMOS full-wave rectifier” Int. J. of Electron., Vol. 93, no.3, pp. 185199, March 2006.
VI. BIOGRAPHIES
Nigar Minhaj received her B.E. in Electrical Engineering in 1987, M.E and
PhD in Electronics Engineering in 1989 and 1994 respectively from Aligarh
Muslim University, Aligarh, India. Currently she is Associate Professor at
University Women’s Polytechnic, Aligarh Muslim University, Aligarh, India.
She had contributed a number of research papers in reputed International
journals. Her current topic of interests is active networks.
75
© 2009 ACADEMY PUBLISHER