THS4140, THS4141

HIGHSPEED FULLY DIFFERENTIAL I/O AMPLIFIERS

SLOS320E − MAY 2000 − REVISED JANUARY 2004

15

POST OFFICE BOX 655303

PRINCIPLES OF OPERATION

theory of operation

The THS414x is a fully differential amplifier. Differential amplifiers are typically differential in/single out, whereas

fully differential amplifiers are differential in/differential out.

Rf

R(g)

R(g)

Rf

_

+

Differential Amplifier

VOCM

_

+

_

+

VCC+

VIN−

VIN+

VO+

VO−

THS414x

Fully differential Amplifier

VCC−

Figure 27. Differential Amplifier Versus a Fully Differential Amplifier

To understand the THS414x fully differential amplifiers, the definition for the pinouts of the amplifier are

provided.

Input voltage definition

V

ID +

V

I

)

–

V

I–

V

IC +

V

I

) )

V

I–

2

Output voltage definition

V

OD +

V

O

)

–

V

O–

V

OC +

V

O

) )

V

O–

2

Transfer function

V

OD +

V

ID

xA

f

Output common mode voltage V

OC +

V

OCM

VOCM

_

+

_

+

VCC+

VIN−

VIN+

VO+

VO−

Differential Structure Rejects

Coupled Noise at the Output

Differential Structure Rejects

Coupled Noise at the Input

Differential Structure Rejects

Coupled Noise at the Power Supply

VCC−

Figure 28. Definition of the Fully Differential Amplifier