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LMH5401: Questions LMH5401 Voltage Gain

Part Number: LMH5401

Dear TEXAS INSTRUMENTS person in charge.

Always I am indebted.

This is Nakayama from Sumitomo Electric Industries, Ltd.


Regarding the subject matter, our company currently assumes high-speed communication (1 Gbps or more),

I am trying to develop a prototype of a board that amplifies voltage amplitude.


As a design requirement for the amplifier board, the input voltage amplitude is about 600mVpp,

The output voltage amplitude is assumed to be 1200 to 2000mVpp.


Also, since high-speed communication is assumed,

Even in bands above 1 GHz (ideally up to around 4 GHz)

It is desirable to obtain stable voltage gain characteristics.


The circuit requires an amplifier element (differential) for amplification,

which seems to meet the requirements of our prototype circuit,

While selecting a differential amplifier,

As a candidate, your company's "LMH5401" was raised.

(It is the most promising candidate because it satisfies stable amplification characteristics from DC to 2 GHz.)


I would like to ask about the characteristics (voltage gain) of the above product.


In the datasheet, the value of voltage amplification gain (GAIN) was described as 12dB.


If the GAIN is 12dB, the voltage amplitude will be about 4 times the input voltage.

The input voltage is amplified too much and the design requirements explained above,

(input voltage 600mVpp → output voltage 1200mV to 2000mV) cannot be satisfied.

* Ideal GAIN should be around 10dB (approximately 3x amplification).


If the GAIN is still 12dB and cannot be adjusted, the requirements cannot be met and this element cannot be adopted.

Checking the graph of the gain characteristics for each frequency described in the latter half of the data sheet,

The gain can be read as if it is adjustable (sorry if it is a misunderstanding)


I thought it would be possible to adjust the GAIN to about 10dB depending on the design of the peripheral circuit.

(An example of the GAIN characteristic graph for each frequency described in the data sheet is

It is a pity that there is no combination that is perfect for 10dB because it is in 6dB increments.)


This amplifier (LMH5401) depends on the design (depending on the adjustment of the element value, etc.)

Is it possible to set the output voltage gain to the desired value (around 10dB)?


Datasheets and how amplifiers work

I apologize for my lack of understanding and rudimentary question,

Please let me know your technical opinion.


Thank you very much.