LMH6505: AGC circuits at V+/V- = 7V/0V

Hello Hirano-San,

  This will depend if an offset is needed. Vg (gain control pin) is not dependent on the power supply configuration of the device; it is instead referenced to the GND pin. What is the range of input voltages into the LMH6505 (Vin on Figure 49)?

Thank you,

Sima

Sima,

Thank you for your response.
Vin amplitude is 11mVpp to 510mVpp, and dc offset is 3.5V.
Could you let them know your recommended circuits, please?

Best regards,

K.Hirano

Hello Hirano-San,

  The input signal into the LMH6505 would be within range; however, there might be an issue into the following stages (within the AGC loop control) due to the DC offset cancellation. I am looking into this a bit more. 

  Also, we have other selections and references for AGC: 

• VCA820 for dB/V gain adjust or VCA822 for V/V gain adjsut
• VCA821 dB/V gain adjust or VCA824 V/V gain adjust (higher bandwidth)

  VCA820 has a simpler version for AGC on page 34 in the datasheet (Figure 85). However there is an issue with this circuit which I address and simulate in this e2e post: https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/1106330/vca810-vca810

Thank you,
Sima 

Sima,

Thank you for your response.
I look forward to receiving more feedbacks from you.

Best regards,

K.Hirano

Sima,

Have you looked into this more yet?
My customer is awaiting your feedbacks.
Please let them know if LMH6505 meets their requirements.
And it does, please show the recommended circuit.

Best regards,

K.Hirano

Hello Hirano-san,

  Is the customer's power supply requirement follow the amplifier stages that are not the LMH6505? As in for example in the AGC recommend circuit, can the customer use dual supply for LMH6714 and LMH6609? 

Thank you,

Sima 

Sima,

After considering LMH6714 and LMH6609 power supply spec, my customer would like to use the following power supplies.
LMH6605 V+ = LMH6714 V+ = LMH6609 V+ = 8V.
LMH6605 V- = LMH6714V- = LMH6609 V- = GND.
Is this acceptable?

Best regards,

K.Hirano

Sima,

I forgot to say dc offset should be changed accordingly.
Vin amplitude is 11mVpp to 510mVpp, and dc offset is V+/2 = 4V.

Or to have margin, do you think the following is better?
LMH6605 V+ = LMH6714 V+ = LMH6609 V+ = 10V.
LMH6605 V- = LMH6714V- = LMH6609 V- = GND.
Vin amplitude is 11mVpp to 510mVpp, and dc offset is V+/2 = 5V.

Best regards,

K.Hirano

Sima,

My customer is awaiting your feedback.
Could you show them TI recommended circuit, please?
Or their requirements can not be achieved by LM6505, LM6605 and LMH6714?

Best regards,

K.Hirano