TL026C

DIFFERENTIAL HIGH-FREQUENCY AMPLIFIER WITH AGC

SLFS007A – JUNE 1985 – REVISED JULY 1990

6

POST OFFICE BOX 655303

APPLICATION INFORMATION

Amplifier A2 inverts V1 producing a positive AGC signal voltage. Therefore, the input voltage to the TL026C

AGC pin consists of an AGC signal equal to:

(6)

R2

R1

V

C

V

AGC

(q)

+ 2

R6

R5

) R6

V

ref

(7)

device to device automatically adjusts the overall bias and makes AGC operation essentially independent of

output voltage limits (see Figures 6 and 7)

The output voltage level desired must fall within the following limits:

1.

Because the data sheet minimum output swing is 3 V peak-to-peak using a 2-k

Ω load resistor, the

user-selected design limit for the peak output swing should not exceed 1.5 V.

2.

The voltage drop of the rectifying diode determines the lower voltage limit. When a silicon diode is

gain calculations for a peak output voltage of 1 V

A peak output voltage of 1 V was chosen for gain calculations because it is approximately midway between the

limits of conditions 1 and 2 in the preceding paragraph.

for maximum TL026C gain change.

* V1

V

C

+

DV

AGC

V

C

+ R2

R1

+ 0.36

0.3

+ 1.2

If R1 is 10 k

Ω, R2 is 1.2 time R1 or 12 kΩ.

Since the output voltage for this circuit must be between 0.85 V and 1.3 V, the component values in

Figures 6 and 7 provide a nominal 1-V peak output limit. This limit is the best choice to allow for temperature

variations of the diode and minimum output voltage specification.