Hi
I am using the regulator TL497 in the case of I(pk)>500mA so I need an external transistor for that but in the datasheet they don't mention how to choose the transistor and its resistors does anyone has an idea about that ?
Datasheet:http://www.mouser.com/ds/2/405/tl497a-405896.pdf

 

You need to choose a pnp transistor that will give you the current over 500mA, the pin10 resistor is to turn the transistor on, so 1k to 10k will do, the pin 13 resistor is for current sense.


Here are some pnp transistors to look at, buy them at a store near your location.
http://cpc.farnell.com/webapp/wcs/s...87614,110199758,110200673,110201939,110203788

 

You need to choose a pnp transistor that will give you the current over 500mA, the pin10 resistor is to turn the transistor on, so 1k to 10k will do, the pin 13 resistor is for current sense.


Here are some pnp transistors to look at, buy them at a store near your location.
http://cpc.farnell.com/webapp/wcs/stores/servlet/Search?catalogId=15002&langId=69&storeId=10180&categoryId=700000010688&sort=P_PRICE&st=Pnp transistors&pageSize=25&showResults=true&aa=true&pf=110137578,110137586,110148370,110148443,110158937,110169571,110187317,110187614,110199758,110200673,110201939,110203788

Thank you, I am not talking about Rcl I mean the other resistor between pad 13 and the base of the transistor and if it is possible can you tell me why the value of the other resistance is between 1k and 10k?

 

Any high value of resistor enough to turn the transistor on to saturate it into conduction, will do, most switching transistors usually have around 100 ohms to 1k on the base,

Try this example

https://www.google.co.uk/search?q=t...AUICCgC&biw=360&bih=512#imgrc=TQdszGGRFINV2M: