Hello Hello,
So, Please bare with me i'm new to this... The Goal is a small handheld (probe) listening device for trouble shooting audio signal flow. it will be powered off of 2x1.5 volt cells and drive a 32 Ohm, 12mW Nom. 20mW Max. transducer (Speaker). I also wanted to have built in Limiting to prevent damage to the device or the listeners ears. I believe i have accomplished this with the addition of D1 & D2 and then softened there effects by adding the voltage divider made up of R6 & R7. (this should give me -22db Apx. "PAD" when R3=2k increasing to 36db Apx "PAD" when R3 = 10k one thing that concerns me is if this compensate for the added gain. -0.425 at 2k and -2.125 at 10k and how to smooth the transition when D1,2 Reach there 0.7V Apx. forward Bias also it doesn't seem right to just calculate the the Gain when D1,2 are biased as you would if R3 and R6 where in Parallel?)
Op Amp Choice: i have looked at a few options in this regard and think i have settled on a TLV2782 or TLV2783 depending on power switching or IC Shut Down method.. what are your thoughts on this IC? Link to Data sheet below.
http://www.ti.com/product/tlv2782
Other design considerations:
The input must be AC coupled to keep any DC Bias from damaging the circuit.
I want to keep current draw to a minimum to extend battery life.
the input signal should be audible anywhere between -40dbu and +4dbu i've been looking at building 3 units for testing each with a deferent input sensitivity; -10dbu, 0dbu, & +4dbu.
all components must be surface mount and the over all size and number of parts must be keep to a minimum.
Thank you very much for having a look at this and i appreciate all the great input i'm sure you will have..
So, Please bare with me i'm new to this... The Goal is a small handheld (probe) listening device for trouble shooting audio signal flow. it will be powered off of 2x1.5 volt cells and drive a 32 Ohm, 12mW Nom. 20mW Max. transducer (Speaker). I also wanted to have built in Limiting to prevent damage to the device or the listeners ears. I believe i have accomplished this with the addition of D1 & D2 and then softened there effects by adding the voltage divider made up of R6 & R7. (this should give me -22db Apx. "PAD" when R3=2k increasing to 36db Apx "PAD" when R3 = 10k one thing that concerns me is if this compensate for the added gain. -0.425 at 2k and -2.125 at 10k and how to smooth the transition when D1,2 Reach there 0.7V Apx. forward Bias also it doesn't seem right to just calculate the the Gain when D1,2 are biased as you would if R3 and R6 where in Parallel?)
Op Amp Choice: i have looked at a few options in this regard and think i have settled on a TLV2782 or TLV2783 depending on power switching or IC Shut Down method.. what are your thoughts on this IC? Link to Data sheet below.
http://www.ti.com/product/tlv2782
Other design considerations:
The input must be AC coupled to keep any DC Bias from damaging the circuit.
I want to keep current draw to a minimum to extend battery life.
the input signal should be audible anywhere between -40dbu and +4dbu i've been looking at building 3 units for testing each with a deferent input sensitivity; -10dbu, 0dbu, & +4dbu.
all components must be surface mount and the over all size and number of parts must be keep to a minimum.
Thank you very much for having a look at this and i appreciate all the great input i'm sure you will have..