Circuit for generating from low voltage edges higher voltage pulses having precise amplitudes and durations

Abstract

A low voltage source of input edges for a pulse of precision duration is applied to an input buffer to provide a low impedance source whose output is AC coupled to positive and negative edge differentiators. Each differentiator briefly drives ON a corresponding normally OFF switch, the pair of which switches serves as an impulse driver and that may be clamped to symmetrical opposing reference voltages. The clamped impulse driver may also be coupled to a bi-stable switch driver that responds to a particular polarity impulse driver voltage by applying thereto through a load resistor a percentage of a power supply voltage of opposite polarity. The bi-stable switch driver changes state each time input edges of alternating polarity are applied to the input buffer. The impulse driver is also coupled to the gates of a complementary pair of MOSFET switches that are in series between precise reference voltages of opposing polarities, and whose common junction may be connected to a current determining resistance whose other end is connected to a using circuit, such as an integrator. The output of the MOSFET switches may be assisted by an auxiliary bi-stable output driver that reduces the amount of load current drawn from those MOSFETs, and thereby reduces errors arising from thermally induced variations in their on resistance.

1 . A method of producing pulses from a sequence of input signal edges that alternate in polarity, the method comprising the steps of: 
 (a) differentiating positive transitions of the input signal edges;    (b) amplifying the differentiated positive transition of step (a);    (c) differentiating negative transitions of the input signal edges;    (d) amplifying the differentiated negative transition of step (c);    (e) alternately charging a capacitance with the amplified differentiated transitions of step (b) and with the amplified differentiated transitions of step (d);    (f) driving a load to a positive power supply voltage with a switched ON first FET when the capacitance is charged to a first polarity;    (e) driving the load to a negative power supply voltage with a switched ON second FET when the capacitance is charged to a second polarity; and    (f) one of the first and second FETs being an N-type FET and the other being a P-type FET.    
   
   
       2 . A method as in  claim 1  wherein the first and second FETs are in series and the polarities of the FETs are chosen to create make-before-break operation.  
   
   
       3 . A method as in  claim 1  wherein the first and second FETs are in series and the polarities of the FETs are chosen to create break-before-make operation.  
   
   
       4 . A method as in  claim 1  wherein the load is a resistor coupled to the input of an integrator and further comprising the step of integrating current pulses formed by the switching of the first and second FETs.  
   
   
       5 . Pulse production apparatus comprising: 
 an impulse driver having an input for receiving a sequence of input signal edges that alternate in polarity, that differentiates the input signal edges into positive and negative impulse transients, and that separately amplifies the positive and the negative impulse transients and presents the amplifications at a common output of the impulse driver;    a capacitance coupled between the common output of the impulse driver and an AC ground;    a complementary pair of FET switches in series with each other, the complementary pair in parallel with a supply voltage, and the gates of the complementary pair of FET switches each being connected to the common output of the impulse driver; and    the junction of the complementary pair of FET switches in series being a pulse output coupled to supply an output pulse.    
   
   
       6 . Apparatus as in  claim 5  wherein the order of the complementary pair of FET switches as they are in parallel with the supply voltage produces make-before-break operation.  
   
   
       7 . Apparatus as in  claim 5  wherein the order of the complementary pair of FET switches as they are in parallel with the supply voltage produces break-before-make operation.  
   
   
       8 . Apparatus as in  claim 5  further comprising a integrator having an input and also further comprising an integrator input resistor coupled between the pulse output and the input of the integrator.  
   
   
       9 . Apparatus as in  claim 5  wherein the peak-to-peak voltage of the output pulse is greater than the peak-to-peak voltage of the input signal edges that alternate in polarity.  
   
   
       10 - 20 . (canceled)