EL2002CM datasheet(7/12 Pages) ELANTEC

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EL2002C

Low Power 180 MHz Buffer Amplifier

Burn-In Circuit

2002 – 10

Simplified Schematic

2002 – 11

Application Information

The EL2002 is a monolithic buffer amplifier built

on Elantec’s proprietary Complementary Bipolar

process that produces NPN and PNP transistors

with essentially identical DC and AC character-

istics The EL2002 takes full advantage of the

complementary process with a unique circuit

topology

Elantec has applied for two patents based on the

EL2002’s topology The patents relate to the base

drive and feedback mechanism in the buffer This

feedback makes 2000 V

ms slew rates with 100X

loads possible with very low supply current

Power Supplies

The EL2002 may be operated with single or split

supplies with total voltage difference between

10V (g5V) and 36V (g18V) It is not necessary

to use equal split value supplies For example

5V and a12V would be excellent for signals

from b2V to a9V

Bypass capacitors from each supply pin to

ground are highly recommended to reduce supply

ringing and the interference it can cause At a

minimum 1

mF tantalum capacitor with short

leads should be used for both supplies

Input Characteristics

The input to the EL2002 looks like a resistance in

parallel with about 35 pF in addition to a DC

bias current The DC bias current is due to the

miss-match in beta and collector current between

the NPN and PNP transistors connected to the

input pin The bias current can be either positive

or negative The change in input current with in-

put voltage (RIN) is affected by the output load

beta and the internal boost RIN can actually ap-

pear negative over portions of the input range

typical input current curves are shown in the

characteristic curves Internal clamp diodes from

the input to the output are provided These di-

odes protect the transistor base emitter junctions

and limit the boost current during slew to avoid

saturation of internal transistors The diodes be-

gin conduction at about g25V input to output

differential When that happens the input resist-

ance drops dramatically The diodes are rated at

50 mA When conducting they have a series re-

sistance of about 20

X There is also 100X in series

with the input that limits input current Above

75V differential input to output additional se-

ries resistance should be added

Source Impedance

The EL2002 has good input to output isolation

When the buffer is not used in a feedback loop

capacitive and resisitive sources up to 1 MHz

present no oscillation problems Care must be

used in board layout to minimize output to input

coupling CAUTION When using high source

impedances (RS l 100 kX) significant gain er-

rors can be observed due to output offset load

resistor and the action of the boost circuit See

typical performance curves

EL2002CM Datasheet(PDF) 7 Page - Elantec Semiconductor

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