DATA SHEET
KH300
To avoid the peaking at low non-inverting gains, place a
Distortion and Noise
resistor R in series with the input signal path just ahead
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.
p
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
First, convert the output voltage (V ) to V
= (V /2√2)
o
rms
pp
2
and then to P = (10log (20V
)) to get output power in
10
rms
R such that the source impedance in parallel with R
dBm. At the frequency of interest, its 2nd harmonic will
be S = (I - P) dB below the level of P. Its third harmon-
p
i
(see Figure 1), plus R equals 175Ω will flatten the
p
2
2
frequency response. For larger gains, R will decrease.
ic will be S = 2 (l = P) dB below P as will the two tone
p
3 3
third order intermodulation products. These approxima-
tions are useful for P < -1dB compression levels.
Settling Time, Offset, and Drift
After an output transition has occurred, the output
settles
very rapidly to final value and no change occurs
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:
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.
2
2
i
R
f
n
2
v
+
n
A
v 2
F = 10log 1+
4kTR ∆f
s
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.
Where v 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
n
noise figure, so ∆f should equal one (1) and v and in
n
Overload Protection
To avoid damage to the KH300, care must be taken to
insure that the input voltage does not exceed (|V | -
should be read directly off of the graph. Below the
breakpoint, the noise must be integrated and ∆f set to
the appropriate bandwidth.
CC
2.5)/A . High speed, low capacitance diodes should be
V
used to limit the maximum input voltage to safe levels if
a potential for overload exists.
If in the non-inverting configuration the resistor R , which
i
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 18µA, can create a large enough input voltage
to exceed the overload condition. It is therefore recom-
mended that R < [(|V | -2.5)/ A ]/(18µA).
i
CC
V
6
REV. 1A January 2004
CADEKA [ CADEKA MICROCIRCUITS LLC. ]
