AD841

REV. B

–8–

Figure 25. Circuit for Driving a Large Capacitive Load

USING A HEAT SINK

The AD841 draws less quiescent power than most precision

high speed amplifiers and is specified for operation without a

heat sink. However, when driving low impedance loads, the cur-

rent to the load can be 4 to 5 times the quiescent current. This

will create a noticeable temperature rise. Improved performance

can be achieved by using a small heat sink such as the Aavid

Engineering #602B.

TERMINATED LINE DRIVER

The AD841 functions very well as a high speed line driver of ei-

ther terminated or unterminated cables. Figure 26 shows the

AD841 driving a doubly terminated cable in a follower configu-

ration. The AD841 maintains a typical slew rate of 300 V/

µs,

which means it can drive a

±10 V, 4.7 MHz signal or a ±3 V,

15.9 MHz signal.

impedance of the cable) minimizes reflections from the far end

characteristic impedance of the cable) may be placed between

the AD841 output and the cable in order to damp any stray sig-

teristic impedance. This will result in a “cleaner” signal, but

amp must supply double the output signal required if there is no

back termination. Therefore the full power bandwidth is cut in

half.

If termination is not used, cables appear as capacitive loads. If

this capacitive load is large, it should be decoupled from the

AD841 by a resistor in series with the output (see above:

Driving a Capacitive Load).

Figure 26. Line Driver Configuration

OVERDRIVE RECOVERY

Figure 27 shows the overdrive recovery capability of the AD841.

Typical recovery time is 200 ns from negative overdrive and

700 ns from positive overdrive.

Figure 27. Overdrive Recovery

Figure 28. Overdrive Recovery Test Circuit

E-20A

20-Terminal Leadless

Ceramic Chip Carrier

12-Lead Metal Can Package

(TO-8 Style)

14-Pin Cerdip (Q) Package

14-Pin Plastic (N) Package

OUTLINE DIMENSIONS

Dimensions shown in inches and (mm).