KH300 datasheet(6/7 Pages) CADEKA

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DATA SHEET

KH300

REV. 1A January 2004

To avoid the peaking at low non-inverting gains, place a

resistor Rp in series with the input signal path just ahead

of pin 6, the non-inverting input. This forms a low pass

filter with the capacitance at pin 6 which can be made to

cancel the peaking due to the capacitance at pin 8, the

inverting input. At a gain of +2, for example, choosing

Rp such that the source impedance in parallel with Ri

(see Figure 1), plus Rp equals 175Ω will flatten the

frequency response. For larger gains, Rp will decrease.

Settling Time, Offset, and Drift

After an output transition has occurred, the output

settles very rapidly to final value and no change occurs

for several microseconds. Thereafter, thermal gradients

inside the KH300 will cause the output to begin to drift.

When this can not be tolerated, or when the initial offset

voltage and drift is unacceptable, the use of a compos-

ite amplifier is advised. This technique reduces the off-

set and drift to that of a monolithic, low frequency op

amp, such as an LF356A. The composite amplifier

technique is fully described in the KH103 data sheet.

A simple offset adjustment can be implemented by con-

necting the wiper of a potentiometer, whose end termi-

nals connect to ±15V, through a 20K resistor to pin 8 of

the KH300.

Overload Protection

To avoid damage to the KH300, care must be taken to

insure that the input voltage does not exceed (|VCC| -

2.5)/AV. High speed, low capacitance diodes should be

used to limit the maximum input voltage to safe levels if

a potential for overload exists.

If in the non-inverting configuration the resistor Ri, which

sets the input impedance, is large, the bias current at

pin 6, which is typically a few pA but which may be as

large as 18

µA, can create a large enough input voltage

to exceed the overload condition. It is therefore recom-

mended that Ri < [(|VCC| -2.5)/ AV]/(18µA).

Distortion and Noise

The graphs of intercept point versus frequency on the

preceding page make it easy to predict the distortion at

any frequency, given the output voltage of the KH300.

First, convert the output voltage (Vo) to Vrms = (Vpp/2√2)

and then to P = (10log10(20Vrms2)) to get output power in

dBm. At the frequency of interest, its 2nd harmonic will

be S2 = (I2 - P) dB below the level of P. Its third harmon-

ic will be S3 = 2 (l3 = P) dB below P as will the two tone

third order intermodulation products. These approxima-

tions are useful for P < -1dB compression levels.

Approximate noise figure can be determined for the

KH300 using the Equivalent Input Noise graph on the

preceding page. The following equation can be used to

determine noise figure (F) in dB:

Where vn is the rms noise voltage and in is the rms noise

current. Beyond the breakpoint at the curves (i.e.,

where they are flat), broadband noise figure equals spot

noise figure, so

∆f should equal one (1) and vn and in

should be read directly off of the graph. Below the

breakpoint, the noise must be integrated and

∆f set to

the appropriate bandwidth.

kTR

log

∆

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