TRF372017: Baseband drive circuit

Hi Maged,

Thanks for your question, we have received and will get back to you. Due to the holiday season, please allow for some delay in our responses.

Thanks,

Aman

Hello, Kang Hsia 

Thanks for your reply, a lot of important suggestions, let me check it, I'll post the block diagram and schematic. 

regards     

Eng. Maged

Hello, Kang Hsia

Sorry for being late, I 've been revised your reply and study some technical data sheets.

First, this is my suggestion block diagram to interface waveform generator (AD9833) with IQ modulator (TRF372017) 

Second, the schematic shall be something like this , first AD9833 then a unipolar to bipolar converter, then LPF

then ,  Single-Ended to Diff. finally IQ modulator

So

regarding to  unipolar to bipolar converter,

I imitate both ti technical documents "SBAA603 and SLAA869   Analog Engineer's Circuit" 

this part will interface between AD9833 with internal resistor 200 Ohm and LPF with both input and output impedance are 50 ohms

and simulation results for both input and output 

is something wrong with this circuit? or do you have some notes about it?

regarding to the second part LPF then Single-Ended to Diff. I used THS4509, like your previous suggestion and the circuit such that 

AND SIMULATION WILL BE 

Also , is something wrong with circuit? do you have notes about it ?

Finally the 100 ohm resistor between BB inputs for TRF372017 as shown in Fig up is this represent RL ?

I'm really sorry for this long post, 

thanks for your interest and help

regards

Eng maged

Also, 

Hello,

Please advise your highest frequency and bandwidth out of the amplifier circuit to the TRF372017. I will need to refer you to our amplifier experts to comment, and need the information to reference you to the associated forum group.

-Kang

Hello

The frequency for TRF372017 will not exceed than 4.2GHz and bandwidth less than 3MHz   

Eng Maged

Please advise the maximum frequency out of the amplifier circuit (i.e. baseband input of the TRF372017, not output). 

Hello

I got it, the maximum baseband is 3MHz

Regards

Hi Maged, 

Could you clarify which part of the circuit you are inquiring about? The differential amplifier circuit or the buffer amplifier circuit? 

Regards,
Ashley

Hello Ashely

actually both, but if I have to choose. The differential amplifier circuit and interfacing it with TRF372017 is more important for me since for buffer amplifier I've referenced with "SBAA603 and SLAA869" .  

Regards,

Maged

Hi Maged, 

In that case, I will move this thread over to this High Speed Amplifier team to further support the differential amplifier circuit you have referenced above as it is using the THS4509. 

They can help to support this further with this device application. 

maged ahmed said:

regarding to the second part LPF then Single-Ended to Diff. I used THS4509, like your previous suggestion and the circuit such that 

AND SIMULATION WILL BE 

Also , is something wrong with circuit? do you have notes about it ?

Finally the 100 ohm resistor between BB inputs for TRF372017 as shown in Fig up is this represent RL ?

Thank you!
Best Regards,
Ashley

Hello Maged,

Our HSAMPs team will look over the thread and provide any additional insight we can offer.

We may have more follow-up questions, thank you for your patience.

Best,

Alec

Hello Alec

waiting to hear from your team.

Regards

Maged  

Hello Maged,

  Thank you for your patience. We reviewed your design and requirements, and have a few comments and suggestions. 

1. Looked into the waveform generator, and it has a voltage output between 38mVpp to 0.65Vpp with a max frequency of 12.5MHz with either a sine, triangular, or square wave output. I am unsure what the DC offset is for the device, but you have your design set to 1.7V. I will assume you will AC couple from output of the generator into the buffer/amplifier prior to your 5th order LPF. 
   
   
2. Your chosen OPA355 is a good choice, but I also recommend looking at these other amplifiers depending on your other specifications: link comparing automotive/catalog qualified amplifiers. In your OPA355 circuit, you have VS+ set to 3.3V and VS- set to 3.2V. The total of 6.5V is below the abs max voltage (7.5V) of the part, but we do recommend operating the device between 2.7V and 5.5V. If you need higher operating power, I suggest looking at the link between OPA814 and OPA817. 
   
   
3. Will you be using the full range of the waveform generator from 38mVpp to 0.65Vpp? If it is the entire range, I suggest this system layout instead: ADS98333 Waveform Generator --> OPA355 at a gain of 2V/V --> 5th order LPF --> Variable gain Fully Differential Amplifier --> TRF372017. The variable gain fully differential amplifier is a catalog of devices we provide which are fully differential amplifiers with gains that can be either altered digitally or via analog voltage. Since you would need single-ended to differential conversion, I would recommend either the LMH6518 or the LMH6881. If you have a specific smaller voltage range, I would then recommend choosing our regular FDAs, as you have chosen the THS4509. I am unfamiliar with TRF372017, but THS4509 could be overkill for a bandwidth of 3.5MHz. I would suggest looking at the THS4551 and THS4541 if you want to use 3.3V power supplies. Otherwise, we also have many options for 5V supply range which can be found at this link.
   
   
4. Simulation of OPA355:
   
   I can recommend a different circuit if your voltage supplies are flexible. Can you work with these supplies: +/-2.5V and you would have to consider your waveform generator's required single 2.3 V to 5.5 V power supply. Or, we can work with single +5V supply for your entire design including your waveform generator. 
   
   
5. THS4509 voltage supply is from 3V to 5V recommended, or 6V max. I believe you are violating the supplies which is the reason for the simulation result. Depending on the answers above, we can redesign with THS4509 or we can help with designing with the variable fully differential amplifiers 

Thank you,

Sima

Hello Sima,

first sorry for being late,

   Thank you for your helpful notes, i'll give my comment in red one by one 

1- "Looked into the waveform generator, and it has a voltage output between 38mVpp to 0.65Vpp with a max frequency of 12.5MHz with either a sine, triangular, or square wave output………."

      Exactly I’m planning to use AC couple between waveform stage and the next

2- "Your chosen OPA355 is a good choice, but I also recommend looking at these other amplifiers depending on your other specifications: link comparing automotive/catalog qualified amplifiers. ……."

         Actually I figured out this point, so I’ planning to use  3.3V as a VS+ and – 1.8V as a VS-   for  OPA 355 since it will be suitable for the required output             voltage swing (1.7+0.6 V to 1.7-0.6V)

3- "If you have a specific smaller voltage range, I would then recommend choosing our regular FDAs, as you have chosen the THS4509. I am unfamiliar with TRF372017,.........." 

      Actually according to datasheet, TRF372017 accept BB input around 0.3V rms with CMV equal to 1.7V, so the output voltage swing (2.3~ 1.1) V is                suitable for IQ baseband  signal

4- “ but THS4509 could be overkill for a bandwidth of 3.5MHz I would suggest looking at the THS4551 and THS4541 if you want to.......... ”

          I couldn’t get this point as per THS4509 datasheet,  BW up to 1900 MHz, or I miss something here ?

5- "THS4509 voltage supply is from 3V to 5V recommended, or 6V max. I believe you are violating the supplies which is ..........."

        I  totally agree with you, so after I submit  previous post I already replaced THS4509 with THS4503 using supply voltage Vs+=5V, VS-=gnd and BW              up to 370 MHz

So finally after these two changes

• Supply voltage for OPA355, VS+ = 3.3V and VS-= 8V
• Using THS4503 with power supply VS+ = 5V and VS-= gnd

  and data, BB voltage signal for TRF372017 equal to 0.3Vrms, BW for THS4503 equal to 370

Do I still need other modifications?

6-" I can recommend a different circuit if your voltage supplies are flexible. Can you work with these supplies: +/-2.5V and you would have to consider your waveform generator's required single 2.3 V to 5.5 V power supply. Or, we can work with single +5V supply for your entire design including your waveform generator"

   Thanks for your proposal, it will be helpful to consider new ideas from your side, i have +5, +3.3,±1.8

thank you for your patience

Regards

Maged

Hello Maged,

  Thank you for your additional comments! I will base the proposed design on your available supply voltages and the TRF372017 input requirements. I should be able to get back to you by end of the week.

Best Regards,

Sima