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[FAQ] Other Devices Information

"Balanced" Mic Pre-Amplifier (PGA2500/INA166?)

Q:

1. Can "bipolar" input and "balanced" be thought of as the same thing?

2. What follow up will I need to narrow down which pre amp is best?

A:

1. A balanced audio interface generally transmits signals through "signal symmetry", that is the two conductors carrying the signal have an equal voltage but an opposite polarity. The idea being that noise coupled into the transmission medium (cable) will have the same polarity on both conductors and will be removed at the receiving side by a differential amplifier. This is the advantage of using the XLR interface for audio cables as opposed to RCAs. I have never encountered the term "bipolar" being used to describe a balanced audio interface. The most common usage of the term "bipolar" in amplifiers is to describe either the input devices of the integrated circuit (Bipolar Junction Transistors or BJTs) or having symmetrical power supplies around a ground reference (e.g. +15V and -15V). It would be useful to know the context in which "bipolar" was used to describe a circuit in order to clarify its meaning. 

2. Both of these parts deliver fantastic performance, the primary difference between them is how the gain is set in the system. The PGA2500 is a programmable gain amplifier and therefore its gain can be configured digitally, by sending commands over an SPI interface. The INA163 and INA166 are entirely analog and the gain is set by changing the value of a resistor between the RG pins. This is often done with a potentiometer that the user can adjust but digital control of the gain is often difficult to accommodate. I would start by asking the customer how they plan to control the gain of the microphones in their system. If it will be in software then the PGA2500 is a better option. 

DSD1702 Information

In page 3 of DSD1702 datasheet, in the “terminal function” chart, it specify the Vcc (analog power supply) should be 5V.

However, at the bottom of same page for absolute maximum rating, it shows Vcc max value is 4V. This is an error. It should read 6.5V, and the absolute maximum rating for Vdd should be 4V. 

We have logged this issue in our system and will fix it on the next revision of this data sheet.

RC4580 current limit

Q: RC4580 current limit

I'm interested in the RC4580 amplifier and want to know if it is short circuit protected. There is no indication that it is protected in the datasheet.

 

If it is not short circuit protected,  what short circuit protected device would be similar in performance and cost? 


A: Re: RC4580 current limit

The absolute maximum output current is 50mA, but the data sheet chart shows the shorted output current is greater than 50mA. Output shorts are not allowed.

 

A: Re: RC4580 current limit

I think that I found what I need using the LM833

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