# Recent content by afr123

1. ### Magnetic switch for disconnecting the circuit

Hi, I have a cirucit operated from a 12V battery. I am designing a circuit for charging the batteries using inductive charging. The cirucit should be disconnected from the batteries when charging and also when not in use. As the system will be in a closed packaging, I want to access the system...
2. ### Units at the Correlator Output

Hello, I have a confusion about a very basic question I guess. I have a pulse of a known waveform measured in volts. I use a matched filter to detect the presence of the waveform in the singal. The impulse response of the matched filter as we know is the time-reversed version of the...
3. ### Output resistance of an audio amplifier

Some concepts are not clear to me. I have a piezoelectric transducer and I have to drive that to generate ultrasonic signals. What I am thinking is to drive it by an audio amplifier and a transformer. I am not really sure whether I need impedance matching here. The piezoelectric input impedance...
4. ### Output resistance of an audio amplifier

Hi, I am using LM4950 audio amplifier and I am interested to know its output impedance. There is nothing mentioned in the datasheet except that it can provide 7.5W at 8 ohm load (at Vdd = 12V, 10% THD, and 1 kHz). How do I calculate the output impedance? Regards
5. ### BER when number of received bits less than transmitted bits

I think I didn't completely understand your point. So basically, the transmitter generate a sequence of chirp signals and then the receiver demodulates those chirp signals using some signal processing. Sometimes I don't detect some chirps (due to factors like noise, threshold setting etc), so I...
6. ### BER when number of received bits less than transmitted bits

Hi, I want to calculate the BER when the number of received bits is less than the number of transmitted bits. For equal number of transmitted and received bits, I can just compare bit by bit and then calculate the BER. The problem is when I miss some bits, then how do I calculate BER. For...
7. ### BMP280 Pressure Sensor Maximum Pressure

Hi, I have interfaced BMP280 Pressure sensor with the Raspberry PI. I measured the atmospheric pressure and it shows the correct value. Then I put the whole setup in a water tight bag and went to maximum 8m depth with 1m increments. The datasheet of BMP280 says that it can measure Max Pressure...
8. ### Sound Transmission loss in water

Hi, I measured the sound pressure levels at different distances using hydrophone as a receiver. Now I want to know where the transmission loss due to spreading is spherical, cylindrical or between the two from the measured data. My data is in volts which can be converted to Pressure using...
9. ### SNR measurements at the output of opamp

okay. I just need to mention that I used this oscilloscope with these settings then the results should match (without considering the internal noise of the oscilloscope itself). The measured values above are at input of the opamp while the gnd of the scope and the tip were shorted. The...
10. ### SNR measurements at the output of opamp

This is DUT. I want to measure the noise at the output of this filter and amplifier. This output of this opamp is connected to 16-bit ADC. I put the gnd and tip at the gnd terminal of DUT. Measured AC-RMS noise = 384uV (duration = 20ms) Vpp = 6.8mV (duration = 20ms) Regards
11. ### SNR measurements at the output of opamp

The opamp is configured as a 4-stage bandpass filter (10kHz - 100kHz) with a gain of 500. What I need is to measure the SNR at the output. My Oscilloscope settings are BW limit: 20MHz AC coupling 5mV/div I only have a high-end oscilloscope from Agilent Technologies to record the data. What I...
12. ### SNR measurements at the output of opamp

Hi, I have a very basic question. I want to calculate SNR at the output of the opamp. First I measured the rms value of the noise without any input using a digital oscilloscope. Then I input a sinusoidal input of 40kHz to the opamp. The voltage at the output was 0-5V. So to measure the SNR I...
13. ### Op amp output voltage

I swept the frequency from 35kHz to 45kHz and using vector network analyzer, I checked the impedance. The ultrasonic transducer is made for around 40kHz freq. Obviously, the impedance was not constant as ultrasonic transducers has capacitive behavior. And yeah, it is not real impedance but...
14. ### Grounding of analog and digital components

Hi, I am designing a circuit but confused about the grounding. I have read analog and TI application notes but still have some confusion. I have one DSP board and with it I plan to connect my own designed board. In my board, I plan to include: 1) DAC for audio output 2) ADC for analog input...
15. ### Op amp output voltage

Okay. Thank you. I have another question. For my design, I plan to connect the output of my opamp to an audio amplifier. And the output of the audio amplifier to the transformer (1:10) to drive the ultrasonic transducer. I have measured the impedance of the transducer and it is around 1000 ohms...