Charge Pump CMOS Circuit
A charge pump CMOS circuit comprises a differential input stage with two parallel circuit branches. Each of the parallel circuit branches has a diode-connected MOS transistor connected in series with a complementary input MOS transistor. There is a common tail current source for both circuit branches. The diode-connected MOS transistors each have their gate/drain node connected to corresponding current sources. The charge pump CMOS circuit is suitable for use in an oscillator.
1 . A charge pump CMOS circuit for use in an oscillator, comprising:
a first diode-connected MOS transistor (MP 3 ) having a source connected to a first common node and a drain and gate connected together (Vb);
a first input MOS transistor (MN 0 ) having a drain connected to the common drain and gate of said first diode-connected MOS transistor (Vb), a source connected to a second common node and a gate receiving a first differential input signal;
a second diode-connected MOS transistor (MN 1 ) having a source connected to said first common node and a drain and gate connected together (Va);
a second input MOS transistor (MP 4 ) having a drain connected to the common drain and gate of said second diode-connected MOS transistor (Va), a source connected to said second common node and a gate receiving a second differential input signal;
a first current source (Ib) connected between said second common node and a third common node;
a second current source (I 1 ) connected between said common drain and gate of said first diode-connected MOS transistor and said third common node; and
a third current source (I 2 ) connected between said common drain and gate of said second diode-connected MOS transistor and said third common node.
2 . The charge pump CMOS circuit of claim 1 , wherein:
said first and second diode-connected MOS transistors (MP 3 , MP 4 ) are P-channel MOS transistors.
3 . The charge pump CMOS circuit of claim 1 , wherein:
said first and second input MOS transistors (MN 0 , MN 1 ) are N-channel MOS transistors.
4 . The charge pump CMOS circuit of claim 1 , further comprising:
a first current mirror circuit including
a first current mirror MOS transistor (MP 2 ) having a source connected to said first common node, a gate connected to the common drain and gate (Vb) of said first diode-connected MOS transistor (MP 3 ) and a drain, and
a second current mirror MOS transistor (MN 6 ) having a drain connected to said drain of said first current mirror transistor (MP 2 ), a gate connected to said drain and a source connected to said third common node; and a second current mirror circuit including
a third current mirror MOS transistor (MP 5 ) having a source connected to said first common node, a gate connected to the common drain and gate (Va) of said second diode-connected MOS transistor (MP 3 ) and a drain,
a fourth current mirror MOS transistor (MN 7 ) having a drain connected to said drain of said third current mirror transistor (MP 5 ), a gate connected to the common drain and gate of said second current mirror MOS transistor (MN 6 ) and a source connected to said third common node, and
an output terminal connected to said drain of said third current mirror MOS transistor (MP 5 ) and said drain of said fourth current mirror MOS transistor (MN 7 ).
5 . The charge pump CMOS circuit of claim 4 , wherein:
said first and third current mirror MOS transistors (MP 2 , MP 5 ) are P-channel MOS transistors.
6 . The charge pump CMOS circuit of claim 4 , wherein:
said second and fourth current mirror MOS transistors (MN 6 , MN 7 ) are N-channel MOS transistors.