CLC522 datasheet(5/8 Pages) NSC

5 / 8 page

Fig. 2 illustrates the resulting CLC522 bandwidths as a

function of the maximum and minimum input voltages

when Vout is held constant at 1Vpp.

Adjusting Offsets

Treating the offsets introduced by the input and output

stages of the CLC522 is easily accomplished with a two

step process. The offset voltage of the output stage is

treated by first applying -1.1Volts on Vg, which effectively

isolates the input stage and multiplier core from the

output stage. As illustrated in Fig. 3, the trim pot located

at R14 on the CLC522 Evaluation Board should then be

adjusted in order to null the offset voltage seen at the

CLC522's output (pin 10). Once this is accomplished, the

offset errors introduced by the input stage and multiplier

core can then be treated. The second step requires the

absence of an input signal and matched source imped-

ances on the two input pins in order to cancel the bias

current errors. This done then +1.1Volts should be

applied to Vg and the trim pot located at R10 adjusted in

order to null the offset voltage seen at the CLC522's

output. If a more limited gain range is anticipated, the

above adjustments should be made at these operating

points.

Gain Errors

The CLC522's gain equation as theoretically expressed

in Eq. 2 must include the device's error terms in order to

yield the actual gain equation. Each of the gain error

Fig. 2

Fig. 3

terms are specified in the Electrical Characteristics table

and are defined below and illustrated in Fig. 4.

GACCU

: error of AVmax , expressed as ±dB.

GCNL

: deviation from theoretical expressed as ±%.

high : voltage on Vg producing A Vmax .

low : voltage on Vg producing

min = 0V/V.

∆V

high

∆V

low

: error of Vg

high

,Vg

low

expresed as ±mV.

Combining these error terms with Eq. 2 gives the "gain

envelope" equation and is expressed in Eq. 7. From the

Electrical Characteristics table, the nominal endpoint

values of Vg are: Vghigh =+990mV and Vg

low

= -975mV.

Signal-Channel Nonlinearity

Signal-channel nonlinearity, SGNL, also known as integral

endpoint linearity, measures the non-linearity of an

amplifier’s voltage transfer function. The CLC522's SGNL,

as it is specified in the Electrical Characteristics table, is

measured while the gain is set at its maximum (i.e.

Vg=+1.1V). The Typical Performance Characteristics

plot labled "SGNL & Gain vs Vg" illustrates the CLC522's

SGNL as Vg is swept through its full range. As can be

seen in this plot, when the gain as reduced from AVmax ,

SGNL improves to < 0.02%(-74dB) at Vg=0 and then

degrades somewhat at the lowest gains.

Noise

Fig. 5 describes the CLC522's input-refered spot noise

density as a function of AVmax . The plot includes all the

noise contributing terms. At AVmax = 10V/V, the CLC522

has a typical input-referred spot noise density (eni) of

5.8nV/

√Hz. The input RMS voltage noise can be deter-

mined from the following single-pole model:

Eq. 8

Further discussion and plots of noise and the noise model

is provided in Application Note OA-23. Comlinear also

provides SPICE models that model internal noise and

other parameters for a typical part.

AVmax

AVmin

low

high

±GCNL

±GACCU

∆Vg

high

∆Vg

low

Fig. 4

Eq . 7

GCNL

GACCU

low

high

low

−±

()

±−

()

±−

()













max

∆

∆∆

dB bandwidth

RMS

=∗

∗ −

()

157

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