Been really busy these past 2 days so apologies for not responding sooner.
Thanks for the info. Every bit helps me to improve...
As per the datasheet you posted, im looking to build the complete circuit in three stages.
is the amplifier which is the darlington configuration.
(as per the datasheet) is then the filter to ensure that only the signals of interest are passed. Hence ive gone for a high pass filter to remove any dc and ambient noise. Given that remotes operate at 36-38Khz, ive gone for the component values below.
converts the pulse to a 0-5V pulse. I thought of using a comparator for this.
While all the stages sounds simple in principle im really struggling
with the filter aspect of things. From my readings things shouldnt be this complicated! I just need to make sure of the following :
For the circuit i posted before this,
When calculating the cuttof frequency f3b=1/(2piRC), do i included the emitter resistor of the darlington pair for R in the formulae? I really think my calculations are incorrect for my filter! Ive used the following, R1=10K, R2=90k and C1=0.0001u (capacitor code 101)