CMOS POOL CIRCUIT

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pool circuit

Explore the new concepts

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Objective

To design a divider and multiplier using pool circuits.Pool is an analog circuit which performsarithmetic operations.

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dividers/multipliers are used inAnalog computational circuits.Analog signal processing.AM modulators.

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In direct implementation

MOS are in triode region.It limits the high frequency of operation.It has high cost.Large power consumption.High area.

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The working principle of pool is based on biological neurons .Where the concentration of a chemical

pool depends on the synthesis anddegradation of chemicals.The synthesis is taken as inward current

the degradation taken as outward current.

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NEURAL POOL

The equilibrium state of

pool concentration isdefined when

Inward current = outward

current

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Pool Circuit Analysis

Arithmetic circuitBasic building block of divider andmultiplier.Aim : Both addition and subtractionDivider=3 , multiplier 11.

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CIRCUIT DIAGRAM

Saturation & Identical Implement adder , subtractor,sign inverter ..using abovecircuit.

Iin=k(Va-Vb);Iout=k(Vc -Vd); Iin=Iout (equil.) k(Va- Vb)= k(Vc -Vd); (Va-Vb)=(Vc-Vd) : k=k

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ADDER

Iin=k(Va-Vo);Iout=k(0 -Vd);Iin=Iout (equil.)

k(Va- Vo)= k(0 -Vd);

Vb=(Va+Vd) : k=k

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SUBTRACTOR

Iin=k(Va- Vo); Iout=k(Vc -0);

Iin=Iout (equil.)

k(Va- Vo)= k(Vc -0);

(Vo)=(Va-Vc) : k=k

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SIGN INVERTER

Iin=k(0-Vo);Iout=k(Vc -0);Iin=Iout (equil.)

k(0- Vo)= k(Vc -0);

Vo=(-Vc) : k=k

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MODIFIED POOL CIRCUIT Both addition and subtraction. Aim to develop divider andmultiplier.

Iin=k(Va- Vo); Iout=k(Vc -Vd);

Iin=Iout (equil.)

k(Va- Vo)= k(Vc -Vd);

(Vo)=(Va+Vc-Vd) : k=k(Vo)=(V1+V3-V4)

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Pool Circuit Results

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The basic idea torealize the divideris to utilize thefollowing equation:(a-b)^2-(a+b)^2=4ab=cwhere b and c areinput and a is theoutput signal.

All transistors arein saturation.

DIVIDER CIRCUIT

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The gate-to-source voltages of the devices M A andMB can be given as:

VGSA = V B - VO + V T

VGSB = VB + VO + V T

The drain currents of M A and M B are:

I1-I2 = K A(VB-VO)^2 - K A(V A+VO)^2

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Advantages of pool circuit

Many functions can be implemented.

No resistors are required.

- avoid power dissipation- reduced area requirement

- makes analysis simpler.

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Improved differential amplifiers are used.

- improve accuracy of results.- increase the range of input voltages.

Regulated current mirrors are used.- high output resistance.

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Disadvantages

Second order effects-Channel length modulation-mobility reduction-transistor mismatch

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Applications of divider andmultiplier

Expected to be useful in analog signal processing applications.

-radar

-communications-industrial controls

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References[1] S. W. Tsay and R. W. Newcomb, "A NEURALTYPE POOL

ARITHMETIC UNIT," Microsystems Laboratory Electrical Engineering Department University of Maryland .

[2] S. Vlassis and S. Siskos, "ANALOG CMOS FOUR-QUADRANTMULTIPLIER AND DIVIDER," Electronics Laboratory,

Department of Physics, Aristotle University of Thessaloniki.

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THANK YOU

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