Save More Power In Handheld Devices

How to save more power when your CPLD device is in idle mode?
Use a very slow clock to reduce toggle rate? Partially disabling the logic inside the device? Well, why not powering off the device?
I came across this interesting article by accident and found it a simple yet smart idea to prolong the battery life of a portable handheld devices. In future, if I have the chance to design a portable product with interactive user interface, this idea will surely be the first one to cross my mind.
If for whatever reason, you have to use a FPGA in a battery-operated product, this article will sure help you more.

OP-AMP Configurations Recall

It has been a while since I last dealed with op-amp. So, it is good to recall some of the most fundamental op-amp configurations, especially when I am dealing with them recently.
In my opinion, op-amp is like logic gates in analog world. You need op-amps to transfer your analog inputs into your desired analog outputs.
The following are some important notes for me, not for you, of course, :)!

Common Names	Op-Amp Circuits	Transfer Functions
Voltage Follower Amplifier		Vout = Vin
Inverting Amplifier		Vout = -(Rf/Rs)Vin
Noninverting Amplifier		Vout = (1+R2/R1)Vin
Difference Amplifier		If R1/R2 = R3/R4, Vout = (Vin+ - Vin-)(R2/R1) + Vshift
Summing Amplifier		Vout = (R2/R1)* (V1+V2-V3-V4)