8.4.1 Mode A

800

:

200 k

:

C1pF

C2

1M

:

R2

R3

Rx

Ry

Ÿ

BUF802

+ 6V

- 6V

+

-

+

-

Precision

Amp

k

+ 6V

- 6V

1k

1k

CLH

CLL

IN

OUT

R1

Input

Figure 8-10. Composite Loop − Mode A

OUT

IN

CLH

I1

R_Bias

Figure 8-11. Internal Schematic − Mode A

As shown in Figure 8-10, the BUF802 is used in Mode A by super-imposing the low-frequency and high-

frequency signal components through R1 and C1 respectively and applying the combined signal at the IN pin.

As shown in Figure 8-11, the combined signal transverses through the BUF802 through the Main path. The pins

associated with Mode B are kept floating. Refer to Section 5 for more details. Since the pins associated with

Mode B are left floating, the Auxiliary path is disabled while operating in Mode A.

In Mode A, the JFET and bipolar transistors in the Main path operate as source and emitter followers to

reproduce the signal applied on IN at the output of the BUF802. The BUF802 can operate from DC to high

frequency and can therefore be used as a standalone buffer. While being used as a standalone buffer, only the

Main path of the BUF802 is used.

8.4.2 Mode B

100 k

100 k

Rb

Rb

Aux_Bias

IN

In_Bias

JFET

I2

I1

RHF

In_Aux

10M

10M

+

-

+

-

Precision

Amp

+

-

Precision

Amp

OUT

Signal_In

R1.R2

(.)

R3,R4

Q1

Diamond

Buffer

G ( Main Path )

Figure 8-12. Internal Schematic − Mode B

R. 800 kŸ

200 kŸ

330 pF

CF 56 pF

R

kŸ

RPOT

Ÿ

+ 6 V

±

V

+

±

Precision

Amp

+6 V

±

V

1 k

1 k

1 k

1 k

CLH

CLL

IN

OUT

R_Bias

10 pF

10 pF

In_Bias

In_Aux

Aux_Bias

10 M

F

F

Input

17.8 kŸ

.

Figure 8-13. BUF802 Schematic − Mode B

The 330 pF input series capacitor shown in Figure 8-13 splits the input signal into a low-frequency and high-

frequency component. These signals are applied to In_Aux and IN respectively. The IN pin controls the output of

BUF802 through the Main path, whereas the In_Aux pin controls the output through the Auxiliary path as shown

in Figure 8-12.

BUF802

SBOS998 – JUNE 2021

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