Arduino 500kHz pwm Capacitor charge and discharge

int transistor = 6;
int pwm_value = A0;
int pause_value = 1;

void setup() {
  pinMode(transistor, OUTPUT);
}

void loop() {
  // Charge Capacitor
  pwm_value = analogRead(A0);
  pwmize(pwm_value);
  
  // Discharge Capacitor
  pause_value = analogRead(A1);
  digitalWrite(transistor,LOW);
  delay(pause_value);
}

void pwmize(int delay_time) {
  for (int a=0; a<1000; a++) {
    digitalWrite(transistor, HIGH);
    delayMicroseconds(delay_time);
    digitalWrite(transistor, LOW);
    delayMicroseconds(delay_time);    
  }
}