hi..need to designa linear power supply with output voltage 20v and current 1A. with all required considerations.suggest proper diodes,transistors and resistors.
For Diodes- you can use the 1N4001 through 1N4007 series. The diodes have identical ratings, except for the peak inverse voltage (PIV), which ranges from 50 V for the 1N4001 to 1000V for the 1N4007. In this relatively low voltage circuit even the 1N4001 is more than sufficient with regard to the PIV rating.
For Capacitances - you can use the formula (C=I T/ Vr -> for the half wave circuit)
(C=IT/2Vr for the full wave circuit) where T is the period of the ac input, I is the dc load current and Vr is the peak to peak ripple voltage
Linear Reg :Vout is 20V and 1A
You must know the Vin Range (or Application Voltage), and decide the power transistor is PMOS or NMOS ,PNP or NPN,and the power transistor application voltage.
If you are a IC designer. you can take care these item
Bonding wire type (Wire number ), thermal problem
(thermal PAD or package) ,fault protection (OCP OTP). Stability.