This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

OPA1652 - JFET or CMOS? + Input current noise density question

Other Parts Discussed in Thread: OPA1652, OPA1662

I have a question about the OPA1652 Input current noise density in the data sheet.
My circuit needs to amplify and filter straight from a sensor with a high Rs of 100K to 200K.  The frequencies of interest are 40KHz to 180KHz.

The data sheet says the current noise is 0.5pA/RtHz which seems high for a JFET or CMOS op amp.  See data sheet page 3.

Then, there is no graph for the input current noise density as there is for the input voltage noise density (Figure 1).  But the "Voltage Noise vs Source Resistance" graph shows the same as resistor noise above 10Kohm Rs, implying the input current noise density is less than 0.5pA/RtHz.  See Figure 3 in the data sheet.

Also, the OPA1662 has an input current noise density of about the same at 0.7pA/RtHz (at 100KHz), but still shows a noise contribution from current noise greater than resistor noise at Rs above 10Kohm.

For example, with a 200K Rs, en would be:

OPA1652 - 4.5nV + (200K * 0.5pA) = 105nV/RtHz

OPA1662 - 3.3nV + (200K * 0.7pA) = 143nV/RtHz

The graph shows around 55nV and 150nV, respectively.  The OPA1662 graph agrees with its table but the OPA1652 graph does not agree with its table.

This seems to indicate that the OPA1652 data sheet has an error.  Either the OPA1652 table is wrong and the input current noise density is less than 0.5pA/RtHz, or the Voltage Noise vs Source Resistance graph is wrong to show the noise as low as resistor noise for the higher Rs values and a lower contribution from the OPA1652's current noise.

Or am I seeing something wrong?

Please let me know if one of these two is wrong, the 0.5pA/RtHz from the table or the graph of Voltage Noise vs Source Resistance.
Also, please send the graph for the OPA1652 Input Current Noise Density vs Frequency if it is available.

I am using an AD8034, but would like to reduce the cost for the next project.  I'm looking at the OPA1652 and the Microchip MCP662 which are both less.  I like the higher Vs capability and the lower voltage noise of the OPA1652.  But I'm concerned about the current noise of the OPA1652, so I need to know what it really is.

Also, the OPA1652 data sheet says it is a "FET-input" op amp which usually means it is JFET. But the simplified circuit and a thread on the website indicates it is CMOS. Is the input JFET or CMOS?

Thanks