EL4083 데이터 시트보기 (PDF) - Elantec -> Intersil

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EL4083

200MHz Current Feedback Amplifier

Elantec -> Intersil 

EL4083C

Current Mode Four Quadrant Multiplier

General Operating Information

IZ Input (Bias Divisor) and Power

Supplies

The IZ pin is a low impedance (k20X) virtual

ground current input It can accept positive

current from a resistor connected to a positive

voltage source or the positive supply The instan-

taneous bias for the multiplier gain core is pro-

portional to this current value Negative applied

current will put the multiplier portion of the cir-

cuit in a zero bias state and the voltage at the pin

will be clamped at a diode drop below ground

The part will respond in a similar manner to cur-

rents from a current source such as the output of

a transconductance amplifier or one of its own

outputs The overall transfer equation for the

EL4083 is

K(IX c IY) IZ e (IXY – IXY) K E 1

As can be seen from the equation the Z input can

serve as a divisor input However it is different

from the other two inputs in that the value of its

current determines the supply current of the part

and the bandwidth and compliance range of the

outputs and other two inputs Table 1 gives the

equations describing these and other important

relationships These dependencies can complicate

and or limit the usefulness of this pin as a com-

putational input The IZ dependence of the im-

pedance of the multiplying inputs can be particu-

larly troublesome See the IZ divider and the

RMS 2 circuit sections of the application note

for some ways of dealing with this

The primary intended use for the Z input is as a

programming pin similar in function to those on

programmable op amps This enables one to

trade off power consumption against bandwidth

and settling time and allow the part to function

within its power dissipation rating over its full

operational supply range (g4 5V b g16 5V)

The E4083 has been designed to function well for

IZ values in the range of 200 mAk IZ k 1 6 mA

which corresponds to IX and IY signal band-

widths of about 50 MHz to over 200 MHz High-

er values of IZ may cause problems at tempera-

ture extremes while lower values down to zero

will progressively degrade the input referred D C

offsets and reduce speed Below about 50 mA of

bias current the internal servo amplifier loop

which maintains the IZ pin at ground will lose

regulation and the voltage at the pin will start to

move negative (see Figure 10) This is accompa-

nied by a significant increase in input imped-

dance of the pin Figure 11 shows the A C band-

width of the IZ input as a function of the D C

value of IZ Figures 6 and 7 show the bandwidth

and 1% settling time of the multiplying inputs

IX and IY as functions of IZ

IX and IY (Multiplier) Inputs and Offset

Trimming

The IX and IY pins are low impedance (IZ depen-

dent) virtual ground current inputs that accept

bipolar signals The input referred clip value is

equal to IZ c 2 while the full scale value has been

chosen to be 1 25 c IZ to maintain excellent dis-

tortion and linearity performance Operating at

higher full scale values will degrade these two pa-

Table 1 Basic Design Equations and Relationships

Positive Supply Current

Negative Supply Current

Power Dissipation (See Figures 4 and 5)

Multipling Input(s) Impedance

Multiplying Input(s) Clip Point

Multiplying Input(s) Full Scale Value

Multiplying Input Resistor Values

(In Terms of Peak Input Signal)

Full Scale Output (Single Ended)

Full Scale Output (Differential)

IZ (Bias) Input Voltage vs IZ

IZ Signal Bandwidth vs IZ

IX IY Signal Bandwidth vs IZ

IX IY 1% Settling Time vs IZ

ISa e 3 4 mA a IZ c 26

ISb e 4 5 mA a IZ c 27

PWR e (aVS b (bVS)) c (4 mA a IZ c 26 5)

RZX e RZY e (32X) c 1 6 mA IZ

IX (clip) e IY (clip) e IZ c 2

IX (fs) e IY (fs)e IZ c 1 25 (nominal)

RX e VX (peak) IX (fs)

RY e VY (peak) IY (fs)

IXY e IXY e IX (fs) c IY (fs) (IZc2)

(IXY b IXY) e IX (fs) c IY (fs) IZ

(See Figure 10)

(See Figure 11)

(See Figure 6)

(See Figure 7)

8

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