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I need to use a TX/RX switch for my ultrasonic sensor. It looks like TX810 is the right one. But before that i have couple doubts from the user guide. Link attached below.
1. Figure 5 of the document shows recovery time with small input signal.
My understanding is that the input given is a combination of 0.25 Vpp followed by 140 Vpp.
The question that i have is, why is there an oscillation of 0.25V in the output even after the input amplitude goes to zero ( i.e after 0.25 micro second).
Could someone pls explain me about this small signal at the output.?
2. Also can you please compare the Figure 6 with Figure 5 and ellaborate whats exactly going on at the output ?
Thanks in advance.
Chuck Smyth, Applications Engineering, HealthTech-Imaging
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In reply to csmyth:
Thanks for the response. Initially i m trying tx/rx of my transducer with the following circuit design.
We are using Capacitance based ultrasonic transducer (CMUT) to oscillate in 17MHz frequency for TX/RX. The same transducer transmits and receives, while the transmitted signal is limited by the bridge diodes in the given circuit, and the received signal must be allowed to reach the transimpedance amplifier, so that i can be seen at the amplifier output.
During transmission the CMUT is excited using 60V DC and 5Vpp ac. During the receiving, the DC is still there but the AC signal goes off. The reflected received signal goes to the bridge diode circuit for further amplification.
In the below circuit, port P1 is for AC pulse, J1 is for DC bias, port P3 is the transducer that sends and receives the signal and port P2 is the output whose scopes are attached below . The second circuit is for powering up the amplifier.
Scope 1- with the transducer connected at P3 port
channel 3 is transmitted signal, channel 1 is received signal at port P2.
Scope 2- without the transducer .
channel 3 is transmitted signal, channel 1 is signal at port P2.
Both the above two scopes looks similar to the figure 5 & 6 of TX810 attached in my previous post.
Does it means that the oscillating signal , that we are seeing from the scope 1 after the TX, is from the received signal (which is suppose to be a small signal)?
Thank you for the previous response.
In reply to LIVINGSTONE ARJUNAN:
I have described my requirement below in detail. Kindly suggest the right component .
i m using 2 ultrasonic transducer that is capacitive based one for transmitting and the other for receiving.
The transmitting signal is AC pulse at 5Vpp ,17MHz with DC bais of 60 V. This transmitted signal is received by the receiver transducer and its been given as an input to OPA 657 amplifier. And i am getting the output, which means the setup works fine. Below is the schematic of TX and RX mode.
Now my intention is to do the same TX/RX using a single transducer whose transmitting signal has to be blocked or limited , before it reaches the op-amp's input and allow only the received signal to the same op-amp input. So i m in need of a switching component which has capability to work as per my requirement. I found TX810 to be a right component for my project. Is there any better alternatives that suits my project needs or TX810 is the best option to go for?
The TX810 is designed specifiically to do exactly what you are talking about. So, I understand your need. The only issue is whether the performance, specifically the overload recovery, is good enough. Is the input to the TX810 at 0V DC after the AC coupling cap? What is the load at the output of the TX810?
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