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A bit further datasheet shows
Input Impedance and Bias Current
Input bias current is measured
with the output held at 1.4V. As with any
simple NPN differential input stage, the LT1016 bias current will go to zero on an input that is low and double on an input that is high. If both
inputs are less than 0.8V above V–, both input bias currents will go to zero. If either input exceeds the positive common
mode limit, input bias current will
increase rapidly, approaching several
milliamperes at VIN = V+.
Op 20-5-2021 om 12:04 schreef G8ZHA
I have built a couple of W1GHz projects: a GPS locked 10MHz
osillator and a 100MHz PLL board. Each of his circuits uses a
LT1116 hi speed comparator to lift the oscilator signal up to 5V
CMOS logic levels to feed the dividers.
On the 100MHz PLL PCB, there is a 3.3V osc, feeding a MC12080
Div by 10 prescaler, AC coupled into the non-inverting input
ofthe LT1116. The inverting input is tied directly to ground. I
can see a nice square wave signal into this pin, about 1.5V
pk-pk, centered on 0V. The outputs, which are open circuit, are
very distorted, see photos.
I thought that this may be because the signal is outside the
common range of 0 - 2.5V for the LT1116, so I biased the input
to the middle of the voltage range but was not successful.
Am I missing something obvious?
I also built the 10MHz version, which feeds the osc straight
into the comparator. I hadn't got a LT1116, so used a LT1016
instead, which has a common mode input range of 1.25 tp 3.75V
range. Again, I biased the input signal to the middle of the
voltage range, but saw the same distored oyutput.
(in the UK, the LT1116 is not available from RS etc)
I am at a loss to understand what is going wrong.