Programmable gain amplifier with glitch minimization

A programmable gain amplifier (PGA), comprising:

• a resistor;
• a plurality of fine stage switches having inputs coupled to corresponding taps on said resistor, said fine stage switches arranged into two or more groups, each group having an output terminal and n-fine stage switches that are capable of being indexed from 1-to-n, said n-fine stage switches having outputs coupled said output terminal for said corresponding group;
• and
• two or more coarse stage switches corresponding to said two or more groups for selecting among said groups, each coarse stage switch having an input coupled to said output terminal for said corresponding group, and each coarse stage switch having an output coupled to an output of the PGA;
• wherein if a selected fine stage switch is closed in a selected group, then another fine stage switch is also closed in one or more unselected groups.

A programmable gain amplifier (PGA), comprising:

• an amplifier;
• a resistor having a first terminal coupled to an output of said amplifier and a second terminal coupled to a reference voltage, said resistor having a plurality of taps between said first terminal and said second terminal;
• a plurality of fine stage switches having inputs coupled to corresponding taps on said resistor, said fine stage switches arranged into two or more groups, each group having an output terminal and n-fine stage switches that are capable of being indexed from 1-to-n and connected to adjacent taps of said corresponding taps, each n-fine stage switch in said groups having an output coupled said output terminal for said corresponding group;
• and
• two or more coarse stage switches corresponding to said two or more groups, each coarse stage switch having an input coupled to said output terminal for said corresponding group, each coarse stage switch having an output coupled an output of the PGA;
• wherein if a fine stage switch is closed in a first group, then another fine stage switch is closed in a second group that is adjacent to said first group.

A method of adjusting the gain of a programmable gain amplifier (PGA), the PGA having a resistor with a plurality of taps and a switch network between the taps and an output of said PGA, the switch network having a plurality of fine stage switches coupled to said plurality of taps, the taps and corresponding fine stage switches arranged into two or more groups of n-fine stage switches capable of being indexed from 1-to-n, and the switch network having a plurality of coarse stage switches for selecting among said groups of n-fine stage switches, the method comprising the steps of:

• receiving a gain control signal that identifies a selected tap of said plurality of taps that is to be connected to the PGA output;
• closing a fine stage switch corresponding to said selected tap in a selected group;
• and
• closing a fine stage switch in each of the unselected groups.

A programmable gain amplifier (PGA), comprising:

• a resistor having a plurality of taps;
• a first group of n-fine stage switches, each fine stage switch in said first group having an output coupled to a first group output terminal;
• a second group of n-fine stage switches, each fine stage switch in said second group having an output coupled to a second group output terminal;
• each fine stage switch in said first group and said second group having an input coupled to a corresponding tap on said resistor;
• said first group of fine stage switches connected to a first group of adjacent taps of said plurality of taps, and said second group of fine stage switches connected to a second group of adjacent taps of said plurality of taps;
• a first coarse stage switch having an input coupled to said first group output terminal, and an output coupled to an output of said PGA;
• a second coarse stage switch having an input coupled to said second group output terminal, and an output coupled to said output of said PGA;
• and
• wherein if a nth fine stage switch is closed in said first group, then a nth fine stage switch is closed in said second group, said nth fine stage switch in said first group and said nth fine stage switch in said second group having a common relative position in their respective groups.

A method of adjusting the gain of a programmable gain amplifier (PGA), the PGA having a resistor with a plurality of taps and a switch network between the taps and an output of said PGA, the switch network having a plurality of fine stage switches coupled to said plurality of taps, the fine stage switches arranged into two or more groups, the method comprising the steps of:

• closing a first fine stage switch in a first group of said two or more groups;
• closing a second fine stage switch in a second group of said two or more groups;
• closing a coarse stage switch that corresponds to said first group;
• opening said coarse stage switch that corresponds to said first group;
• and
• closing a second coarse stage switch that corresponds to said second group.