Best Precision, Low Power JFET Amplifier on the Market

[TheOne]

Just received this in my mailbox, looks very good.

AD8641

The AD8641 is a low power, precision JFET input amplifier featuring 250 µA max supply current, 1 pA max input bias current, and 750 µV max offset voltage. High source impedance, low bias current, and low supply current are key to applications, such as ECG/EKG monitors, sleep monitoring, and blood analyzing instruments. The AD8641 is also ideal for applications utilizing multichannel boards that require low power to manage heat, such as photodiodes, precision active filters, and industrial controls. The ability to swing rail-to-rail at the output enables designers to buffer wide output swing devices in single-supply systems.

Low Supply Current: 250 µA max
Very Low Input Bias Current: 1 pA max
Low Offset Voltage: 750 µV max
V Noise Density 28.5nV/rtHz
Single-supply Operation: 5 V to 26 V
Dual-supply Operation: ±2.5 V to ±13 V
Rail-to-rail Output
Unity Gain Stable
No Phase Reversal
SC70 Package

https://www.analog.com/en/prod/0,2877,AD8641,00.html

 

[audioguru]

It has a nice low offset voltage and supply current, but I wouldn't call it the best, it is fairly noisy.

 

[Russlk]

For low noise, I like SSM2135 from Analog Devices. 5.2nV/rt Hz at 1 kHz.

 

[TheOne]

It has a nice low offset voltage and supply current, but I wouldn't call it the best, it is fairly noisy.

They said it not me! That was the heading of the promotional email I received from Analog Devices calling it "Best Precision, Low Power JFET Amplifier on the Market" as mentioned in Volume 5, Issue 1 THE ANALOG DEVICES SOLUTIONS BULLETIN **broken link removed**

 

[Oznog]

Ain't no such thing as "the best". That's an illusion.

I want cheap, readily available, low offset, low noise, low power, high bandwidth, high voltage, low input impedance, rail-to-rail input and output, and high output current.

Now which order those are in depends entirely on my application. Most of the time at least half those items don't matter at all. Sometimes one or two of those items is extremely important.

 

[audioguru]

-------- low input impedance, --------

Hi Oznog,
I hope that was a typo!

You failed to mention the feature of "lack of crossover distortion" which is very important in a low-power opamp. Look at the old LM324 low-power (the first?) opamp. Its output transistors don't even conduct more than half the time to keep the idle current down. Truely class-B. Sounds horrible.

 

[Juglenaut]

I'd say high input impedence.