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I have designed the attached circuit for detecting how long an ultrasonic pulse need to to travel a distance. the input signal is going to be from a 40 k ultrasonic receiver. First stage is 40k Band pass - 1k pass band - differential MFB filter with a gain of 2.25dB at Center frequency. In feedback path of differential amplifier I have used 33k instead of ideal value of 31.6k . I will appreciate some useful comments on how this circuit can be improved. Also I am going to design a PCB using smt components. I need suggestion to improve the circuit like adding capacitor to supply rail and VOCM which will reduce power supply noise etc.
Your circuit is straightforward; however, a few changes may help you better achieve your performance goals:
I hope this helps.
PA - Linear Applications Engineering
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In reply to Thomas Kuehl:
Thank you for your response. I have designed this circuit using NI Multisim. i have used 33k as i don't have 31.6 available in my lab. a gain of 1000 was for worst condition. I hope i will not require more than 200 at worst. i wan't to reduce stages at this will add to the latency. Some delay would be introduced by each stage of amplifier. one clarification regarding TLV2460 oscillation. Is the oscillation would be due to bypass capacitors? I was not aware of TLE2426 kind of component.
In reply to Ajit Singh1:
The power supply bypass capacitors that you place on the 1/2 Vcc output level appear as a capacitive load to the TLV2460 output. Adding a bypass capacitance with common values of 10 nF,100 nF, or more, is considered a large capacitive load. The capacitive load, in conjunction with the amplifier's output impedance, result in a pole that adds additional phase shift to the feedback loop. This reduces the phase margin and if at some frequency the margin goes to zero degrees and the amplifier gain is great than 1 V/V, the circuit becomes an oscillator.
Different operational amplifier models will have a different phase margin at the unity-gain cross frequency and their output impedance vs. frequency can be very different as well. Both are significant factors in determining whether a particular operational amplifier will be stable when driving a capacitive load. You can usually find a graph in an operational amplifier's data-sheet indicating phase margin vs. load capacitance, or overshoot vs. load capacitance that will provide a good indication of stability.
PA - Linear Applications Engineering
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