EL2082CS datasheet(8/16 Pages) ELANTEC

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EL2082C

Current-Mode Multiplier

Applications Information

Contd

The output current could be terminated witha1k

X load resistor to achieve a nominal voltage gain of 1

at the EL2082 but the IOUT load and stray capacitances would limit bandwidth greatly The lowest

practical total capacitance at IOUT is about 12 pF and this gives a 13 MHz bandwidth witha1kX

load In the above example a 100

X load is used for an upper limit of 130 MHz The operational

amplifier gives a gain of a10 to bring the overall gain to unity Wider bandwidth yet can be had by

installing CIN This is a very small capacitor typically 1 pf–2 pF and it bolsters the gain above

100 MHz Here is a table of results for this circuit used with various amplifiers

Operational

Power

3 dB

01 dB

Amplifier

Supplies

CIN

Bandwidth

Peaking

EL2020

620

34 MHz

56 MHz

EL2020

15V

620

40 MHz

74 MHz

EL2130

620

73 MHz

11 MHz

10 dB

EL2030

15V

620

93 MHz

12 MHz

13 dB

EL2090

15V

240

60 MHz

10 MHz

05 dB

EL2120

220

57 MHz

10 MHz

04 dB

EL2120

15V

220

65 MHz

11 MHz

03 dB

EL2070

200

2 pF

150 MHz

30 MHz

04 dB

EL2071

15K

240

2 pF

200 MHz

30 MHz

EL2075

620

2 pF

270 MHz

30 MHz

15 dB

Maximum bandwidth is maintained over a gain range of a6to b16 dB bandwidth drops at lower

gains If wider gain range with full bandwidth is required two or more EL2082’s can be cascaded with

the IOUT of one directly driving the IIN of the next

The EL2082 can also be used with an I

xV operational circuit

Gain eb

VGAIN

RIN a95X

2082 – 14

Inverting

EL2082 a Op-Amp

The circuit above gives a negative gain The main concern of this connection involves the total IOUT

and stray capacitances at the amplifier’s input When using traditional op-amps the pole caused by

these capacitances can make the amplifier less stable and even cause oscillations in amplifiers whose

gain-bandwidth is greater than 5 MHz A typical cure is to add a capacitor Cf in the 2 pF – 10 pF range

This will reduce overall bandwidth so a capacitor CIN can be added to regain frequency response The

ratio CfCIN is made equal to RIN Rf

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